First I'd have to decide if I'm actually going to go or not. If not I can always blame it on work.. Being on call 24/7 can have it's uses even if it's a pain in my ass when there is something I actually want to do.
Upon arriving the first thing I'd do is look for where the alcohol is, then a corner to hide in till I've had a few in me while searching for people I know.
I'll hang around them and try and join any conversation that may be going on till they tell me to stop standing beside them cause I make them feel uncomfortable. At which point I'll usually wander off and find somewhere to sit down and go back into observe mode.
Go into a deer caught in headlights state if whatever came over and tried to give me a lapdance. And it's not that I'd be paying attention to whatever but rather thinking about how I am now somehow the center of everyones attention and I have no clue what to do when it comes to getting out of it but I'd be frantically searching my mind looking for one.
Then I'd find a different corner to hide in while keeping a distance from anything that remotely looks like a dance floor since I can't dance at all.
After I find a corner to hide in I'll start fending off random people who come up and try and start conversations for the fear that I'll say something stupid and regret it later, only to end up doing so.
Around that time I'm at the point where all I want to do is just go home so I'll make a dash for the exit.