The context of your post—college apartment, parties, loud music—leads me to conclude that your intention is not necessarily an über-high-quality dedicated listening / HT room; you just want things to sound good. Based on that, I would offer the some basic rules of thumb:
L-C-R Symmetry: Set up the front and center loudspeakers symmetrically along one of the walls. L and R should be equidistant from their respective side walls. C in the center.
Sub Placement: Put it wherever it sounds best. Assuming there is a desire to keep it along the same wall as the L-C-R loudspeakers, there should be a spot somewhere between the corner and the C loudspeaker where the sub sounds best. If you have more flexibility concerning placement, move it around to different spots until it sounds best to you.
Treatment: I could certainly offer advice on room treatments and such, but I would assume that with < $1K to put towards the system, you probably aren't going to have much in the way of money for treatments. So, if you want to tame some of the room sound (might sound muffled or "boxy," particularly if you have carpet on the floor), you can arrange large bookcases and wall hangings to diffuse some sound. Absorption can be added in the form of (e.g.) hanging blankets. Placement is not going to be hugely critical for your application, but the symmetry rule does (sort of) apply here as well, especially for movie watching. What this means is don't put all the absorption on the left wall with a bunch of bookcases on the right wall. Mix it up.
Other than that, be sure to leave room for the keg!
