2) Turning conversation into a game helps; asking "what's the most interesting conversation we can have?" or focusing on getting to know just two or three people at a party instead of being overwhelmed by the whole group.
3) I agree with Derek Sivers's comment that, correct me if I'm wrong, tolerance for social situations is a skill that you can build up over time, like your ability to focus.
4) It can be useful to have some autopilot topics; see Kaj Sotala's notion of cached thoughts, http://lesswrong.com/lw/2co/how_to_always_have_interesting_c..., stories you're really good at telling, or funny things you've seen (a guy on the street wearing gladiator sandals is one i've been telling recently)