As far as tf2 is concerned, it took me a REALLY long time to start making friends. I think it was like a year before someone decided to add me as a friend. The trick there is to become a regular on a server and do something to get noticed (being really good or doing some extremely goofy stuff like taunt killing). Alternatively, you could just start adding people yourself and hope someone sticks.
In general, if you want to make friends over games, you just have to start talking. If you say/do something wrong, they're not going to care. Besides, you shouldn't worry about what other people think of you. Just jump in and start having fun.
Check out the L4D2 thread and you'll find some people there who are setting up times to play that. Join on in.
Also, if you want to add me on steam, here's my id:
Steam Community :: ID :: DOOMTRAIN
I haven't played too many games recently, but that doesn't mean I won't if you ask me.