Praise be to Allaah.
First of all we ask Allah, may He be exalted, to bless your efforts and make them weigh in the balance of your good deeds; we ask Allah to help all the Muslims to strive for this religion.
Then we advise you to pay attention to some important matters in calling this person to Islam and teaching him its rulings, such as the following:
It is essential to start with him by teaching him the meaning of the Shahaadatayn (twin declaration of faith), because it is the key to Islam and summarises it. Explain to him Tawheed (the Oneness of Allah), which is the basis of Muslim success in this world and in the Hereafter, so that his heart will become attached to Allah, may He be glorified and exalted. Teach him that absolute servitude is only to Allah, may He be glorified and exalted, and submission to Him means obeying Him and ridding oneself of all burdens of whims and desires.
Among the useful books which explain these matters is Tareef Aam li Deen al-Islam (A General Introduction to Islam) by Shaykh Ali al-Tantaawi.
You have to direct him towards the Book of Allah, may He be glorified and exalted, and encourage him to read it, ponder it and think about its meanings, for it is light and guidance that Allah sent down for mankind, with which He grants them peace of mind and makes them steadfast in faith. It is all blessing and goodness and reward, and it has a great impact on hearts and minds that is experienced by everyone who reads it. Allah says (interpretation of the meaning):
Indeed, there has come to you from AllÃ¢h a light (Prophet Muhammad) and a plain Book (this Qur'Ã¢n).
Wherewith AllÃ¢h guides all those who seek His Good Pleasure to ways of peace, and He brings them out of darkness by His Will unto light and guides them to a Straight Way (IslÃ¢mic Monotheism)
You should teach him some of the Qur'aan and a little of how it was revealed and some of its soorahs and verses.
Then teach him something about our Prophet Muhammad (blessings and peace of Allah be upon him), about his birth, how he grew up and how his mission began; about how the call to this great religion started. Then tell him about his migration to Madinah and how he put up with all kinds of hardship for the sake of conveying guidance and truth to mankind. Then tell him about the character of the Prophet (blessings and peace of Allah be upon him), that we have access to today through his Sunnah and the saheeh hadeeths. Anyone who wants to read about this noble Messenger from the most trustworthy sources should read the Saheehs of al-Bukhaari and Muslim, and books of the Prophetic Sunnah in general and books of Seerah (Prophet's biography). In these books he will find details of the life and teachings of the Prophet (blessings and peace of Allah be upon him):
Books that we recommend for this purpose include:
Mukhtasar Saheeh al-Bukhaari by al-Zubaydi
Mukhtasar Saheeh Muslim by al-Mundhiri
Riyad al-Saaliheen by al-Nawawi
Al-Raheeq al-Makhtoom by al-Mubaarakfoori
All of these have been translated into English and have been published.
[All these titles are available from Darussalam Publishers, Riyadh, KSA]
You also have to teach him a little about the five pillars of Islam: the Shahaadatayn (twin declaration of faith), salaah (prayer), zakaah (obligatory charity), sawm (fasting) and Hajj (pilgrimage). And teach him about the six pillars of faith: belief in Allah, His Angels, His Books, His Messengers, the Last Day, and the divine decree, both good and bad.
If you set aside for this Muslim brother some sessions to talk about each of these pillars, and read with him some books that speak of them, that will be very helpful and beneficial, in sha Allah.
Try to teach these pillars without going into details of differences of scholarly opinion. Stick to the main principles that all Muslims are agreed upon. Point out to him that there are some differences concerning some details, but they are not blameworthy differences and they have not divided the Muslims, praise be to Allah; rather these are genuine differences based on different interpretations of the shari texts and occurred for a reason that Allah has decreed by His wisdom; the one who gets it right will have two rewards and the one who gets it wrong will have one reward.
Another useful book concerning this matter is the book entitled Ma la yasa al-Muslim Jahluhu (What the Muslim cannot afford to be unaware of) by Dr Abd-Allah al-Muslih and Dr Salaah al-Saawi. It is a very useful book that describes the main aims of Islam and its principal rulings.
Some of your teaching him should be devoted to explaining prohibitions in Islam, so that he will understand that the boundaries of prohibitions in Islam are quite small, and everything beyond that is permissible, in sha Allah. He should be aware of the major sins on which there was consensus that they are haraam: shirk (associating others with Allah); witchcraft or magic; killing a soul whom Allah has forbidden to be killed except in cases dictated by Islamic law; consuming riba (usury); consuming the wealth of orphans; disobeying one's parents; and so on. It is also a good idea for him to learn about some of the minor sins, so that he can avoid them and keep away from them too, especially since one who comes to Islam is usually very sincere and motivated to adhere completely to the rulings of Islam.
You can make use of the book al-Kabaa'ir (Major Sins) by Imam al-Dhahabi [available in English from International Islamic Publishing House (IIPH), Riyadh, KSA]. It is a very useful and comprehensive book on this topic.
It is also very important to explain to him that our Islamic religion is a religion that encourages good interactions with people; it encourages the best and noblest of attitudes and characteristics and it regards a good attitude (towards people) as one of the things that are most effective in helping a person to enter Paradise. Islam teaches that by having a good attitude (towards people), one may attain the level of one who fasts and prays at night. Truthfulness, honesty, sincerity, keeping one's word, tolerance, generosity, kindness, compassion and other good characteristics are all part of the essence of religion. That is summed up in the words of the Prophet (blessings and peace of Allah be upon him): I have been sent to complete noble (attitudes and) characteristics. (Narrated by al-Bukhaari in al-Adab al-Mufrad, 273; and by al-Haakim in al-Mustadrak, 2/670 - he classed it as saheeh and al-Dhahabi agreed with him. It was classed as hasan by al-Albaani in al-Silsilah al-Saheehah, 45.)
One of the most important things you should pay attention to when teaching him is the issue of raqaa'iq (heart softening reports etc) and actions of the heart (i.e., spiritual matters). The heart is like a garden; if a person does not take care of it, it will be taken over by thorns and weeds. The heart (in a spiritual sense) becomes clean by learning of the greatness of Allah, may He be exalted, and developing the fear of His punishment, hope for His reward, love for Him, may He be glorified, and longing to meet Him. The Muslim should also learn about sincerity (towards Allah), repentance, humbleness, asceticism, piety, respecting the sacred limits, patience, contentment, gratitude, certainty of faith, and putting one's trust in Allah. All of these are important acts of worship of the heart that one has to pay attention to and take care of. The one who pays attention to learning their reality will find great delight and joy in faith; the one who neglects them is neglecting a great deal of good.
The books of the great scholar Ibn al-Qayyim teach about actions of the heart and shed light on these matters. One of the most important of these books is Madaarij al-Saalikeen. But we recommend reading its abridged version by Shaykh Abd al-Munim al-Izzi.
Finally, it is also important to teach him something about the falseness of other religions, especially the religion that he used to follow, so as to increase his certainty about Islam and to protect himself against any specious argument that he may encounter. Then he will see how great is the favour that Allah bestowed upon him when He guided him to Islam and the true religion.
We think that these ideas are sufficient to help in teaching Islam. Although they may appear to be numerous and lengthy and difficult, it is up to you how long or short to make them. You can limit it to what is appropriate to the learner and to you, or you can make it longer if you have enough time.
If the difference in languages between you and him is preventing you from reaching the desired goal, you have no choice but to seek the help of someone who can translate for you, or you can use books and audiovisual materials that are translated into both Arabic and English. You can find some by clicking on the following link:
Or one of you can make the effort to learn the language of the other.
We ask Allah to help and guide us and you.
And Allah knows best.