Get a group of people together (have it even between both sexes or have the female outnumber the males slightly)
Get a bunch of alcohol
Party, joke, have fun. Don't do anything weird, dumb, or corny.
Go out, party some more, and have everyone return to the initial place.
Party, joke, and drink more.
Watch people drop out slowly (eventually you will too).
Wake up extra early (about 4:30am)
Locate the one girl you found attractive and had positive interaction with throughout the night.
Go lay beside her, and if she doesn't oppose, make a move.
Sneak away from the rest of the passed out bodies.
Sex shall commence.
I noticed a pattern and several nights have ended like this for me. I'm not guaranteeing this will work, but I have had many successful nights like this.
Good luck in your endeavors.