Well, if your main interests are "geeky things" how much should you pretend to be interested in X, or Y, or whatever it is that popular "cool" people talk about? Besides, I thought "geek" was "cool" now. So long as you don't go overboard, and find ways to interface with the other people's interests and not just your own, you should be fine.

I think a true "geek" is defined as someone who is so obsessed with one or two things that they have trouble having a normal conversation with people of differing interests. So finding things to talk about is probably as easy (or difficult) as broadening your field of interest, while still being yourself. Read a newspaper or something. There's plenty of stuff to talk about in there.

It all depends on who you hang out with, you need to learn to gauge the other people's interests and respond accordingly, without getting bored yourself.