Da'wah

I had a discussion with my friends regarding the subject of Da`wah. Some said that it is obligatory (Fard, like praying five times a day) on every Muslim to give Da`wah; others said it is not (Fard, but it is recommended (Mustahabb). What is the correct Islamic position in the light of the Qur'an and Sunnah?

Scholar of Islam, As-Salamu `alaykum. I am a Muslim girl who wants to tell people around the world about Islam. I have many friends who are non-Muslims and I want to tell them about my beloved religion. But I do not know the right way or what shall I tell them firstly. I hope you help me. Thanks.

Is tabligh ok for doing daawah?