“If greatness of purpose, smallness of means, and outstanding results are the three criteria of human genius, who could dare to compare any great man in modern history with Muhammad?” Alphonse de Lamartine
Samuel Parsons Scott understood part of the charm of the Prophet’s character when he wrote:
“The glories which invest the history of Islam may be entirely derived from the valor, the virtue, the intelligence, the genius, of man. If this be conceded, the largest measure of credit is due to him who conceived its plan, promoted its impulse, and formulated the rules which insured its success. In any event, if the object of religion be the inculcation of morals, the diminution of evil, the promotion of human happiness, the expansion of the human intellect, if the performance of good works will avail in the great day when mankind shall be summoned to its final reckoning it is neither irreverent nor unreasonable to admit that Muhammad was indeed an Apostle of God.” 
What Samuel Parsons Scott missed, Reverend ProfessorMontgomery Watt a biographer of the Prophet Muhammad grasped or was it a Freudian slip? He high lighted above all virtues the Prophet’s trust in God:
“The more one reflects on the history of Muhammad and of early Islam, the more one is amazed at the vastness of his achievement. Circumstances presented him with an opportunity such as few men have had, but the man was fully matched with the hour. Had it not been for his gifts as a seer, statesman, and administrator and, behind these, his trust in God and firm belief that God had sent him, a notable chapter in the history of mankind would have remained unwritten.” 
A good place for the non-Muslims to start learning about the Holy Prophet Muhammad is a movie named the Message: Mohammed: Messenger of God (1976) Rated PG.
The back cover states, “After seeing a vision of the Angel Gabriel, Mohammad calls to the people of Mecca to cast aside the 300 idols of Kaaba and worship only one God. Starring Anthony Quinn and Irene Papas, this breathtaking historical epic about the birth of the Islamic faith took six years to prepare and more than a year to film. It received an Academy Award nomination for Best Original Score.”
The movie can be watched at the following links:
The stage I is defined by me as those non-Muslims who want to know about the Prophet Muhammad and are not keen to just find the negative stuff. In this stage, I suggest to watch a few documentaries. My main suggestion is to watch or read on and in the words of Sir Francis Bacon, “Read not to contradict … but to weigh and consider.” After you have watched the movie,
the Message,the next movie or documentary I suggest is a history channel biography of the Prophet Muhammad:
In stage II read some of the positive things that the non-Muslim writers have written about him and I have a Google-Knol for you:
Now you are ready to read some biographies of the Prophet Muhammad. I suggest two. First let me introduce an author:
Encylopaedia Britannica states about Sir Muhammad Zafrulla Khan:
“Sir Muhammad Zafrulla Khan was a Pakistani politician, diplomat, and international jurist, known particularly for his representation of Pakistan at the United Nations (UN).
The son of the leading attorney of his native city, Zafrulla Khan studied at Government College in Lahore and received his LL.B. from King’s College, London University, in 1914. He practiced law in Sialkot and Lahore, became a member of the Punjab Legislative Council in 1926, and was a delegate in 1930, 1931, and 1932 to the Round Table Conferences on Indian reforms in London. In 1931–32 he was president of the All-India Muslim League (later the Muslim League), and he sat on the British viceroy’s executive council as its Muslim member from 1935 to 1941. He led the Indian delegation to the League of Nations in 1939, and from 1941 to 1947 he served as a judge of the Federal Court of India.
Prior to the partition of India in 1947, Zafrulla Khan presented the Muslim League’s view of the future boundaries of Pakistan to Sir Cyril Radcliffe, the man designated to decide the boundaries between India and Pakistan. Upon the independence of Pakistan, Zafrulla Khan became the new country’s minister of foreign affairs and served concurrently as leader of Pakistan’s delegation to the UN (1947–54). From 1954 to 1961 he served as a member of the International Court of Justice at The Hague. He again represented Pakistan at the UN in 1961–64 and served as president of the UN General Assembly in 1962–63. Returning to the International Court of Justice in 1964, he served as the court’s president from 1970 to 1973.
He was knighted in 1935. He is the author of Islam: Its Meaning for Modern Man (1962) and wrote a translation of the Qur’an (1970).”
The biography by him, Muhammad: Seal of the Prophets can be read at the following link:
The second biographer that I want to introduce here is byHadhrat Mirza Bashiruddin Mahmood Ahmad (1889-1965), who was mentor of Sir Zafrulla Khan. He led the Ahmadiyya Muslim community from 1914 till 1965, as Khalifatul Masih II. He was one of the greatest Muslim thinkers. The community progressed remarkably during his leadership. The biography by him,
Life of Muhammadcan be read at the following link:
Now you are also ready to visit the official page about the Holy Prophet Muhammad, may peace be on him, by the Ahmadiyya Muslim Community:
The Final Stage or Stage IV If now you admire the Holy Prophet Muhammad to some degree or already are a Muslim then here is the final segment to enhance your understanding of the character of the Greatest of the sons of Adam. You see him through the eyes of his most devoted follower, who is none other than the Founder of the Ahmadiyya Muslim Community. Here is a collection of excerpts from his writings and there is a detailed chapter about the Prophet of Islam, Muhammad, my peace of Allah be on him:
Here I will like to share a few samples:
I always wonder how high was the status of this Arabian Prophet, whose name was Muhammad, thousands of blessings be upon him. One cannot reach the limit of his high status and it is not given to man to estimate correctly his spiritual effectiveness. It is a pity that his rank has not been recognized as it should have been. He was the champion who restored to the world the Unity of God which had disappeared from the world; he loved God in the extreme and his soul melted out of sympathy for mankind. Therefore God, Who knew the secret of his heart, exalted him above all the Prophets and all the first ones and the last ones and bestowed upon him in his lifetime all that he desired. He is the fountainhead of every grace and a person who claims any superiority without acknowledging his grace, is not a man but is the spawn of Satan, because the Holy Prophet has been bestowed the key to every exaltation and he has been given the treasury of every understanding. He who does not receive through him is deprived forever. I am nothing and possess nothing. I would be most ungrateful if I were not to confess that I have learnt of the true Unity of God through this Prophet. The recognition of the Living God we have achieved through this Perfect Prophet and through his light. The honor of converse with God, through which we behold His countenance, has been bestowed upon me through this great Prophet. The ray of this sun of guidance falls like sunshine upon me and I continue illumined only so long as I am adjusted towards it. [Haqiqatul Wahi, Ruhani Khazain, Vol. 22, pp. 118-119].
O all ye who dwell upon the earth, and O all human souls that are in the east or in the west, I announce to you emphatically that the true reality in the earth is Islam alone, and the True God is the God Who is described in the Qur’an, and the Prophet who has everlasting spiritual life and who is seated on the throne of glory and holiness, is Muhammad, the chosen one [peace and blessings of Allah be on him]. The proof of his spiritual life and holy majesty is that by following him and loving him we become recipients of the Holy Spirit and are favoured with the bounty of converse with God and witness heavenly signs. [Tiryaq-ul-Qulub, Ruhani Khaza’in, Vol. 15, p. 141]