Be handsome, charasmatic, confident, and make her laugh. Ez.
Honestly though, whenever I concoct scenarios in my head then shit rarely pans out. I do best with women when I'm not trying to overly impress them or win their hearts. Think it has to do with giving off better vibes like seeming content with yourself and not being wizardly desperate. You want to seem enticing to be around, and you do that by being fun, warm, and empathetic with others (smile and listen). Don't drown yourself in self imposed pressure or expectations, unless you like anxiety and self sabatoging things.
I know tha struggle; it's hard to be laid back when you so badly want some of dat ass
Also, I wouldn't even be worried about this girl until something more serious is established. Go to the party just to meet people and have fun. You can't really plan this shit.
BTW I just farted on my girl so take that as you will