You're asking the Queen of Social Awkwardness here. It depends on the situation. Most social situations make me nervous, unless I know most or all of the people involved. I generally avoid things like cities, malls, and parties where I don't know most of the people. I also get antsy in large groups, even if I do know most of the people. I do not like crowds. Especially in close proximity. If I have to squirm through a sea of people to get somewhere, I will freak out.
I usually just try to go along with it and wait until it's over. If I'm out in public, I keep moving and do what I need to do so I can get out of there. If I'm out in public (especially places like Walmart during the day and the mall) too long, the sensory overload (from all the people, lights, colors, noise, etc.) is kind of overwhelming. Then I withdraw and kind of go into zombie autopilot mode, where I walk around in a daze, not speaking more than a word or two, and I focus on getting out of there. I usually snap out of it pretty quickly after I leave, or if I distract myself with food. (Eating usually works to distract my mind from uncomfortable situations.)
If I'm at some social gathering where I don't know most of the people (tagging along with a friend to a party or something like that), I'll either follow my friend around until we leave (usually not saying anything unless there are a few people I know there) or sit off to the side, watching people. If I'm off to the side, not interacting with anyone, sometimes I'll start to get really uncomfortable, and if there are a lot of people, I kind of freak out and have to leave. This happens very rarely, fortunately.
Basically, the more talkative I am, the more comfortable I am.
Oddly enough, I don't mind addressing a group of people (giving a speech or presentation or whatever), and I don't get "stage fright" or anything like that. Interacting with people individually is what makes me nervous.