In Islamic tradition, what actions or reasons will put you to spend eternity on Hell?

I'm a Catholic and I'm stuck with an atheist in [a discussion](https://plus.google.com/b/103989487441001641495/103989487441001641495/posts/bqXF4TKgtLm) regarding, according to the atheist folk, illogical result receiving the consequences of choosing not to believe in something, as in: *I can't fly out of my car if I don't fasten my seatbelt, because I don't believe I'll get in a crash.* Basically, he thinks that I would spent eternity on *Islamic* Hell because I don't believe in its existence or I don't believe in the *Islamic* God. In Catholicisms, we have very good defined teachings on these regards, about what is Hell and how you get there (to put in some way), But for the sake of our conversation, **I would like to know what actions or reasons will put you to spent eternity on Hell, according to the Islamic Tradition?** I have tried to explain to him that Muslims profess to hold the faith of Abraham, and together with us [The Catholic Church] they adore the one, merciful God, mankind's judge on the last day. But he keeps using the distinctive. Pax et bonum.