Ways of calling Non-Muslims to Islam
11-3-2012 | IslamWeb
Question:
I live in France and often speak with disbelievers. Some of them have good manners and attributes similar to those of Muslims. Sometimes I have the urge to call them to Islam. Am I permitted to do so, given that my religious knowledge is limited? What should I start with?
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
We thank the questioner for his concern for Islam, and for calling others to it and wanting good for them. Allaah The Almighty ordered us to call to Islam with wisdom, encouragement and good reasoning, and to argue with disbelievers with gentleness and kind preaching. Allaah The Almighty Says (what means): {Invite to the way of your Lord with wisdom and good instruction, and argue with them in a way that is best.} [Quran 16:125]
Concerning the people of the Book (Jews and Christians), Allaah The Almighty Says (what means):
• { And do not argue with the People of the Scripture except in a way that is best, except for those who commit injustice among them, and say, "We believe in that which has been revealed to us and revealed to you. And our God and your God is one; and we are Muslims [in submission] to Him."} [Quran 29:46]
• { Say, "O People of the Scripture, come to a word that is equitable between us and you - that we will not worship except Allaah and not associate anything with Him and not take one another as lords instead of Allaah ." But if they turn away, then say, "Bear witness that we are Muslims [submitting to Him]."} [Quran 3:64]
Coming to your question, it is obligatory for every competent Muslim who has accepted Allaah The Almighty as God, Islam as their religion and Muhammad, sallallaahu ‘alayhi wa sallam, as the Prophet and Messenger, to call non-Muslims to Islam and to call non-observant Muslims to adhere to Islam. Allaah The Almighty Says (what means): {Say, "This is my way; I invite to Allaah with insight, I and those who follow me.} [Quran 12:108] Thus, the person who follows the Messenger, sallallaahu ‘alayhi wa sallam, has to call others to this great religion; however the way it is done varies from one person to another, depending on the person's qualifications and position.
In fact, adopting the exalted manners of Islam is one of the most important means of giving Da‘wah, since actions speak louder than words.
You should start by explaining that there is only one religion of Allaah, the religion of all prophets, beginning with 'Aadam (Adam) 
and ending with Muhammad, sallallaahu ‘alayhi wa sallam. All Messengers came to preach the Oneness of Allaah the Almighty.
Sometimes, it may be necessary to start with something else, such as describing the virtues of the Islamic Sharee‘ah (Islamic law), its conformity to man's innate disposition and how it satisfies a person's physical, mental and spiritual needs. For example, the Islamic Sharee‘ah prohibits whatever harms man's body and mind, such as intoxicants. Indeed it prohibited the consumption of any small amount, since this leads to drinking more, as not all people can control themselves, and the Sharee‘ah is meant for all people. Besides this, there is a great deal of underlying wisdom whether known or unknown.
Allaah Knows best.