Huge halloween party this weekend, never been to a party this huge?

Yo guys. I'm 17 and im going to a 150+ person party this weekend. I have never been to a party with over 30 people and i'm confused on what to do when i get there. I mean, the party is from 10-2, i have no idea what i'll be doing there for 4 hours. I'm going with two friends and there will definitely be alcohol and weed, i might take a few sips to loosen up. I mean, i'm not the kind of guy that approaches random people(unless maybe i drank) but yeah. Me and my friend are going to try and wingman and get some girls, but im a bit nervous of the outcome. Any ideas? and thanks