“Invite (mankind, O Muhammad) to the Way of your Lord (i.e. Islam) with wisdom (i.e. with the Divine Inspiration and the Quran) and fair preaching, and argue with them in a way that is better. Truly, your Lord knows best who has gone astray from His Path, and He is the Best Aware of those who are guided.” [Surah An-Nahl (16) :125]
This ayah tells us how to do dawah. Here’s a short but beautiful article that explains the method as outlined by this ayah.