How do you make a conversation last a while?

There's so much awkward silences all the time when i talk with friends.. and we always seem to run out of stuff to talk about. Whenever i try to ask random questions, they all just stare at me like i'm some weirdo or something.. lol. I don't know, maybe i am lol. Anyway, how do you make a conversation last for a while? Like.. the whole recess would be nice :)