I'd probably flit from group to group to say my hellos. Settle on the people I like about halfway through and engage in *deep* *meaningful* conversation. Or just fun talk. Break off periodically to water myself with some alcohol. Say hi to more people or bye. Find it too noisy for quiet talk. Leave early with some special people.
I'm spending the entire day trying to figure out a reason not to go, even though a lot of times I wind up enjoying myself if I can get out the door.
Once I'm there, I stick like glue to the people I know well, and don't really talk to new people unless one of these unfortunate glue people is also in the conversation. I look around and feel self-conscious that I am not mingling and I worry that everyone is looking at me and wondering why that weird guy isn't talking to anyone. If there is an activity like a game, that is when I can relax a little and interact. Maybe even be a little bit of a clown. An activity can act as a buffer and make interpersonal conversations a little less nerve-wracking.
Observing others, which means being on the lookout for people I know. Talk to them, avoiding anyone I don't know. And if someone I don't know starts a conversation, I keep my answers very short or even sarcastic and scare them away. On the way home, I'll hate myself for that
I'm a bit quiet at first at parties - I'll happily greet you if I know you, or even if I've seen you around somewhere before, but I'm not so good at striking up conversations with complete strangers. I don't know where to start, so I'll only really end up speaking to you if I've been deliberately introduced to you and there's some point of similarity I can start with. Then it's usually okay.
I hate to cling, so I'll happily listen to the conversation of complete strangers (or, in dire situations, feign deep interest in some inanimate object) in order to avoid chasing the people I know about the place.
Later on I might venture out and introduce myself to some people, or get into deep/enthusiastic conversations with people I know.
I'm usually one of the last ones there (I tend to enjoy the evening more as it goes on), unless there's a specific reason I have for leaving.