What is the ruling on dawah (preaching) in Islam?

Correcting the wrong doers by hand or by preaching is for the ones who have the chance to do it. You should prevent the people you can influence and rule over from doing wrong by your hand or by preaching. It is also possible that the people in authority prevent the wrong-doings by force in the cases where they transgress the limits of others’ freedom. However, you cannot force anybody about Islam. Because there is no compulsion in religion.

Please click the following links for further information:

http://www.islamandquran.org/fatwas/should-we-hurt-people-who-do-not-fast-in-ramadan.html

http://www.islamandquran.org/fatwas/should-i-put-pressure-on-my-family-to-practice-islam.html