From this discussion we can hopefully know and follow the Prophet of Islam (S.A.W.) better than before.

1- Prophet (S.A.W.) at breast and his childhood
Prophet Muhammad (S.A.W.) was breastfed by his mother Amena (A.S.) in the first three (or seven according to some historians) days after his birth. Afterwards, as a famous Arabian tradition, a nurse was chosen to breastfeed and take care of him outside the city in desert of Arabia. There were a number of reasons for this tradition:
First, children would grow stronger and healthier in desert. Second, since those who lived in deserts had far less communication with foreign people, children could learn the Arabic language purely and without foreign accents. Third, children would be protected from deadly diseases that prevailed within the cities.
Historians believe that the Prophet (S.A.W.) had two nurses:
1. Thuwaybah Aslamiah: To the end of her life, she gained very high respect from the Prophet (S.A.W.) and his wife Khadijah (A.S.)because of nursing and breastfeeding the Prophet (S.A.W.). The Prophet (S.A.W.) was greatly grieved by her demise.
2. Halimah Sa'diah: The daughter of Dhu'ayyab, along with one of her three daughters took care and nursed the Prophet (S.A.W.). The story that she was selected as the nurse of the Prophet (S.A.W.) is briefly mentioned as follows.
Four months after the birth of the Prophet (S.A.W.), all the nurses of Bani Asad tribe came to Mecca to breastfeed the Prophet (S.A.W.). The Prophet (S.A.W.) drank the milk of none but Halimah; thus she became the Prophet's (S.A.W.) nurse.
Halimah explains that with the entrance of Prophet Muhammad (S.A.W.), blessings showered her life such that their property and herd increased daily. Although drought had spread throughout the deserts and cities, Halimah's sheep were healthy and full of milk. Their shriveled trees prospered and grew back green leaves. The camels regained their milk. Furthermore, a number of ill people who came to their house were cured because of the presence of Prophet Muhammad (S.A.W.).
Prophet Muhammad (S.A.W.) stayed with the Bani Asad tribe for five or six years till he grew up. During this period, Halimah took him to visit his mother, Amena (A.S.), three times and the last time she did not take him back.
It has been narrated that when the Prophet (S.A.W.) and Khadijah (A.S.)got married, Halimah came to the Prophet (S.A.W.) and complained about the drought. The Prophet (S.A.W.) gave her some sheep and camels and she returned to her family. After the appointment of the Prophet (S.A.W.), Halimah and her husband came to the Prophet (S.A.W.) and converted to Islam.

2- The adolescence period
When Prophet Muhammad (S.A.W.) reached the age of six, his mother took him to Yathrib (present day "Medina") so he could visit his relatives and his father's grave. They stayed there for one month.
Upon their return to Mecca, Lady Amena (A.S.)passed away. After her demise Abd al-Muttalib (PBUH), the Prophet's (S.A.W.) grandfather and the master of Quraish who had the glory of the kings and the majesty of the prophets, took the responsibility of Prophet Muhammad (S.A.W.). It has been said that there was always a carpet placed near the Kaaba for Abd al-Muttalib (PBUH). No one else dared to sit on the carpet in respect of Abd al-Muttalib (PBUH), however when the little Muhammad (S.A.W.) joined their gatherings, Abd al-Muttalib (A.S.)would place him on the carpet next to himself and would say: "I swear by Allah that he has a high rank. I seem to view a day where he will become your master."
When the Prophet (S.A.W.) became eight years old, Abd al-Muttalib (A.S.)passed away as well. This incident made the Prophet (S.A.W.) very sad.
After that Abu Talib (PBUH), the Prophet's (S.A.W.) great uncle and the master of Quraish, accepted to look after him. He, like his father, Abd al-Muttalib (PBUH), looked after Muhammad (S.A.W.) carefully. Although Abu Talib (A.S.)was not rich, he and his honorable wife Fatimah bint Asad (the mother of Imam Ali (PBUH)), tried their best in looking after Muhammad (S.A.W.).
His presence in his uncle's house was not ordinary. Signs of his greatness could be seen everywhere. His entrance to their house brought bountiful blessings to the house of Abu Talib (PBUH). Lady Fatimah the daughter of Asad has said, "From the moment that Prophet Muhammad (S.A.W.) entered our home, the tree, which had dried up for years, prospered and offered fruits."
Abu Talib narrates that they would hear Prophet Muhammad (S.A.W.) praying at nights. Though it was against the custom of Arabs to remember Allah (SWT) while eating, the little Muhammad (S.A.W.) would not start eating or drinking unless reciting the name of Allah (SWT). He would also end his meal by thanking Allah (SWT), the exalted.

2-1- The travel to Shaam
Quraish's businessmen used to go to Shaam and Yemen every year. Abu Talib used to go with them from time to time. Prophet Muhammad (S.A.W.) attended one of these trips to Shaam with his uncle when he was 12 years old.
Abu Talib was the Prophet's (S.A.W.) guardian after the demise of Abd al-Muttalib (PBUH). In the trip, their caravan rested in the city of "Basri".
A great Christian monk named Bohayra had been living in Basri for many years. Unlike every year, Bohayra came out of his monastery and invited the passing caravan for a meal. While the others were having their meal, Bohayra seemed to be seeking something. Finally, he found what he was looking for in the young Muhammad (S.A.W.). Bohayra was carefully watching his actions and behaviors. After everyone finished their food, Bohayra came to the Prophet (S.A.W.) and asked him couple of questions from his past and other issues. Then he looked upon the Prophet's (S.A.W.) shoulder and found a speckle like he had expected (which later became known as the seal of Prophethood). Bohayra told Abu Talib that this young man would become a great person. He also made a suggestion to Abu Talib (A.S.)to return Prophet Muhammad (S.A.W.) back to his hometown in order to be safe from the Jews.

3- The adulthood period
3-1- The youth agreement
Another important aspect of Prophet Muhammad's (S.A.W.) life before his appointment to prophecy was his enrollment in "the youth agreement".
All tribes in Mecca were related to each other, thus they created treaties between each other to insure the security from attacks. However, for a stranger this was not the case. There was no one to protect a stranger if he had been oppressed.
A man came to Mecca from another town to do some business. Aas Ibn Wa'el, a citizen of Mecca, purchased the man's materials and didn't pay anything in return. The man went to the tribe of Quraish and asked for help, but no one helped him. As a result of this event a group of youth from Quraish gathered and agreed to stop any oppression on strangers. They named the agreement as "Helf al-Fodul". Being one of the main members of establishing this agreement, Prophet Muhammad (S.A.W.) joined the agreement. Later on he regarded it as an excellent event.

3-2- Lady Khadijah (PBUH)
Before discussing Prophet Muhammad's (S.A.W.) marriage with Lady Khadijah (PBUH), let us briefly discuss her character.
She is the first woman who accepted the invitation of Prophet Muhammad (S.A.W.) and converted to Islam.
According to most historians, she was 68 when Prophet (S.A.W.) moved from Mecca to Medina. Her father was Khuwaylid Ibn Asad and her mother was Fatimah bint Za'idah. Lady Khadijah (A.S.)was related to the Prophet (S.A.W.) from her mother's side.
Some of the researchers have said that Fatimah al-Zahra (A.S.)was her only child; however, most scholars say that she had other children as well.
Lady Khadijah (A.S.)was known as a clever person and she had great morality. Moreover, at that time, it was common amongst Arabs to disrespect women and kill their daughters. In such a period however, Lady Khadijah (A.S.)was famous for titles such as "the pious" or "the Lady of the women of Quraish".
She was one of the richest merchants of Quraish. She used to lend some goods to other merchants who went to other cities such as Yemen and on their return they would share the profit of that business. Although most great merchants of Quraish were willing to marry Lady Khadijah (PBUH), she chose to marry Prophet Muhammad (S.A.W.) who was financially in a lower class. After marriage, she devoted all her wealth in spreading Islam. Prophet Muhammad (S.A.W.) said: "Khadijah's wealth was the most useful wealth I ever had." In the 6th year after Prophet's appointment, when Muslims were surrounded in an area called "She'eb Abu Talib", Lady Khadijah (A.S.)used her wealth and power among Quraish to help surrounded Muslims. She spent all of her wealth for Muslims to the extent that before her demise, she had nothing left.
She was one of the greatest women of the world and her rank is as high as the great Mary (PBUH), mother of Prophet Jesus (PBUH). Prophet Muhammad (S.A.W.) says about her: "Four greatest women of the world are: Khadijah daughter Khuwaylid, Fatimah bint Muhammad, Mary bint Emran and Asyeh bint Masher, the wife of Pharaoh."
It has been narrated several times that, Gabriel, the angle of revelation, inspired to the Prophet (S.A.W.) and brought Allah's (SWT) salute for Prophet Muhammad (S.A.W.) and Lady Khadijah (PBUH). This inspiration indicates the great rank of Lady Khadijah (PBUH), because –according to the Holy Quran– Allah (SWT) salutes to his Prophets (PBUT).
Gabriel said: "O Muhammad! Salute to Khadijah from Allah". Prophet told Khadijah (PBUH): "This is Gabriel who has brought Allah's salute and peace for you. Khadijah (A.S.)replied: "Allah is all peace; peace is from Allah and my salute to Gabriel."
Lady Khadijah (A.S.)had a great value in the eyes of the Prophet (S.A.W.) to the extent that he did not marry a second woman while she was alive. The year that she passed away, was coincident with the demise of Prophet's uncle Abu Talib (PBUH). As a result that year was called "the year of sadness." After her demise, the Prophet (S.A.W.) regarded her many times as a great woman.
Aisha, one of the Prophet's wives, narrates: "The Prophet never left our house unless he reminded well of Khadijah." Aisha also narrates: "Whenever, Prophet Muhammad slaughtered a lamb he would say: 'Send this to friends of Khadijah.' Once I asked for the reason of this action and he replied: 'I like friends of Khadijah as well.' "
Considering her high position, it might be easier to realize why she gained the glory of being the Prophet's wife and the honor of being mother of Fatimah al-Zahra (PBUH), the Lady of all women of the worlds.

3-3- Prophet's marriage (S.A.W.) with Lady Khadijah (PBUH)
As mentioned in the previous part, Lady Khadijah (A.S.)was one of the wealthiest merchants of Quraish. She dispatched some men to different cities to trade; afterwards, she would get her share from the profit of their business.
When Lady Khadijah (A.S.)was informed of Prophet Muhammad's (S.A.W.) truthfulness, moral virtues, and his trustworthiness (as he was well-known for), she offered him to go to Syria for trade. She also gave him a larger share than the rest men.
Prophet Muhammad (S.A.W.) accepted this offer and left for Syria; he was being accompanied with Meysara, Lady Khadijah's (A.S.)special servant.
When they arrived in Syria, Prophet Muhammad (S.A.W.) came down in the shadow of a tree near a monastery. A monk asked Meysara: "Who is the man under that tree?" Meysara replied:" He is of Quraish tribe and from Mecca." The monk said: "I swear to Allah that he is no one except a Prophet."
Prophet Muhammad (S.A.W.) sold what he had brought; he bought some other material and then returned to Mecca. In this journey, all businessmen made profit, especially Prophet Muhammad (S.A.W.) who made more than others. Once they returned, Lady Khadijah (A.S.)asked Meysara about Prophet Muhammad (S.A.W.); he said that whatever he did was orderly, logical and wise. He also narrated the happenings throughout the journey and said: "When one of the traders asked him to swear to Laat and Ozza, the two famous idols in Mecca, he refused to do that and said: 'To me, nothing is inferior to Lat and Ozza.'"
Once Lady Khadijah (A.S.)became aware of these incidents, she sent a messenger to Prophet Muhammad (S.A.W.) to express her proposal for marriage. She wanted to marry him because of his dignity amongst family, truthfulness, moral virtues, and trustworthiness.
Once Prophet Muhammad (S.A.W.) was informed of this issue, he sent his uncles to house of Lady Khadijah (A.S.)to propose for her hand in marriage. In the proposal session, Abu Talib, the Prophet's uncle, praised Allah (SWT) and then spoke of the virtues of Prophet Muhammad (S.A.W.). He proposed marriage on behalf of Prophet Muhammad (S.A.W.) to Lady Khadijah (PBUH). Lady Khadijah (A.S.)accepted the proposal and got married to Prophet Muhammad (S.A.W.). At that time, Prophet Muhammad (S.A.W.) was twenty-five years old, and according to some narrators Lady Khadijah (A.S.)was 40. Other narrators, however, record that Lady Khadijah (A.S.)was younger.

3-4- Putting Hajar al-Aswad in its place
Another important event that occurred before the Prophet's mission was the replacement of Hajar al-Aswad in its place. It has been recorded in history that even before Prophet Muhammad's (S.A.W.) appointment the house of Allah (SWT) (Kaaba) was greatly revered by the Arabs. The Prophet (S.A.W.) and some of his ancestors used to do rituals around the Kaaba.
One year, there was a flood in Mecca which destroyed the walls of Kaaba. Quraish, who took the control over this house, decided to repair it. Once they built the walls, a serious dispute raised amongst them, which was going to cause a bloody war. Each tribe wanted the honor of putting the sacred stone of Hajar al-Aswad in its place. Finally an old man who was highly respected by the Quraish tribe suggested that the first man, who entered the mosque area, should become the judge between them. Everyone accepted this suggestion. Meanwhile, Prophet Muhammad (S.A.W.) entered the mosque and the great men of Quraish accepted that he should be the judge.
The Prophet (S.A.W.) commanded them to widen a peace of cloth on the ground. Then he put Hajar al-Aswad on it and called the head of every tribe to take one corner of the cloth.
When they picked up the cloth by the wall, the Prophet (S.A.W.) took the stone and put it in its place. With this wise judgment he put an end to the probable bloody war.
This event shows us that although he was only 35 years old by that time, the Prophet (S.A.W.) was greatly honored by the Quraish and they all agreed on the honesty and trustworthiness of him.

4- The moral characteristics of the Prophet (S.A.W.)
By looking at the life of the great men and their spiritual characteristics, we may know them and their distinguishing characteristics better. The study of different stages of Prophet Muhammad's (S.A.W.) life could give us a chance to know more about his moral characteristics and also may help us to follow his path as an ideal human.
It should be noted that what we say here is a little part of his moral characteristics and we will consider this case more deeply in an article titled as: "Moral Characteristics of the Prophet (S.A.W.)".
In short, his forty-year life period before the appointment was associated with chastity and honesty, trustworthiness and rightness, doing good with the poor and the lower, hatred towards the immoralities within the society along with its custom of idol worshiping. His high moralities and generosity in his behaviors gained the praise of all, to the extent that Allah (SWT) praised him in the Holy Quran for his high moralities. The Prophet (S.A.W.) was nicknamed as "the trustworthy" from the beginning of his youth, thus people trusted him to watch over their properties.
Mostly everyone was against his mission as the Prophet (S.A.W.), but no one doubted in his trustworthiness and thus he continued to secure their properties. Despite the enmity that existed toward him in the city, no one doubted his honesty. Therefore when he decided to migrate from Mecca to Medina, he appointed Imam Ali (A.S.)to pay the debts and to return the properties to their owners.
The Prophet (S.A.W.) never accompanied the people of Mecca in their wining, dining, and unethical nightly parties. Due to the great suffer he endured in that society, he would head towards the cave of Heraa to worship Allah (SWT) for long periods. (You may refer to the article of "The Appointment of the Prophet (S.A.W.)" for more information).
He always named Allah (SWT) before eating, and never ate meat that was not properly slaughtered. Like other prophets, he spent part of his youth as a shepherd. Being a shepherd had great impact on the prophets. It allowed them to separate themselves from the bad deeds of the society; it taught them to endure the difficulties, and it increased their faith in Allah (SWT) as they saw the power of Allah (SWT) and the order He has arranged for nature.
As noted in the section "The Prophet Muhammad's (S.A.W.) Marriage", the Prophet (S.A.W.) spent part of his youth doing trade. It was his high moral characteristics that attracted Lady Khadijah (A.S.)towards himself and eventually led to their marriage.