There is no special procedure to convert to Islam, or any prerequisites, as there is in other religions. The moment you are convinced that the essential teachings of Islam are true, you are a believer in the sight of God. In order for other people to know this you must declare your beliefs by saying the declaration of faith (shahadah) which is: “I declare that there is no other god besides Allah and I declare that Muhammad is His servant and Messenger.” These exact words are not required so anything reflecting that meaning suffices. This verbal declaration is only necessary for others to know you are a Muslim for social purposes as well as legal purposes like marriage, inheritance distribution, receiving a Muslim burial, etc.
What the Qur’an Says
“If anyone desires a religion other than Islam, it will never be accepted, and in the Hereafter he will be with the losers.” (Qur’an 3:85)
What the Scholars Said
Imam Taftazani said: Whosoever believes with the heart but does not declare with the tongue (iqrar bil lisan) is considered a believer in the sight of Allah, but not according to the judgments of this world (Sa’d al-Din al-Taftazani, Sharh Al-Aqidah An-Nasafiyyah, 190)
It is recommended to go to a knowledgeable Muslim (preferably a scholar) who can teach you the basic beliefs of Islam and guide you on what to say to declare your Islam in front of witnesses. Visiting your local, trusted mosque is important and will both help you find a knowledgeable Muslim and help you become part of the greater Muslim community.
Shaykh Mustafa Umar