So the night is going well.
Learn to play beer pong, flip cup, and some card games before you show up. They'll help you meet and connect with people which will make you have fun.
Don't overdo it.
You can not socially afford to throw up or black out. Let others drink for you. There can be atime and place to get crazy, but this is not that time. You are not ready yet! If you are the guy who ruins Suzy Swanson's dress with your vomit, everyone will know it Monday morning. If you break Johhny Football Star's leg when you fall on him, you will get sued. If you burn down Jimmy Rich Kid's vintage-sports-car filled garage - you will go to jail. And Jimmy will not invite you back to his parties. D'oh!