How to keep a cinder block apartment warm in winter!?

My best friend and I are moving into a small, out-of-college-dorms- apartment that unfortunately has cinder block walls that are painted white. I've read reviews about the apartment complex & the biggest complaint was the insulation. I move in next month but I want to be prepared. I don't want a high heating bill because I'm only a student! I was wondering if there is any CHEAP ways to insulate a cinder block apartment? Also I wanna know what the recommendation is for temps to keep the thermostat at so keep the bill low. The apartment is in Colorado if that has any affect. I've lived on my own before but I lived with 3 other people so the bills were always less than $20 each, but since it's just me and another person, I'm kind of freaking out. Any tips would be great.