Before you buy lights, make sure your school allows them. My school didn't allow a variety of lights (esp the string, or twinkle-style lights) because they're a serious fire hazard. Tons of girls brought those in freshman year and had to throw them out because they couldn't use them. No need to waste that money!
Also, I'd suggest talking to your roommate to figure out what each of you is buying, for a few reasons. The first being that you don't want/need 2, 3, or 4 of everything, obviously. Secondly, (this mostly applies to bedding), you don't wanna have two patterns or colors that totally clash and will make your head hurt. I remember one room in particular freshman year that was just so mismatching it was painful to be in there for more than 5 minutes. So ya, keep that in mind as you start planning!!