Are you on the ground floor? If not, leave the door open and fan on; it's going to use way less energy than your AC unit. I recently got the "DTE Insights" app through DTE Energy to track my daily electricity usage and was shocked at how much more energy the AC uses than everything else in the house,
combined!
I'll also second the window blackouts. I had foam-backed foil leaned onto the windows and could regulate my apartment temperature pretty well. The people below me always kept it really hot in their apartment, though, so with the foil turned inward, I rarely had to use heat (even in freezing weather).
Go to LED lights if you can, and find the lowest wattage. I found a 2W candelabra bulb to use over my kitchen table in the apartment, and it was just enough to see what I was doing. Just go and really evaluate how much lighting you really need, and downsize where you can. Five lamps dropping 10 watts for 3 hours a day is saving over 1kWh per week!
Also, I'm sure it's obvious, but TV's, Xbox's, and other electronics eat up energy too, so put them on a power strip and turn them off. Of course that can be a challenge if you have someone else in the house who doesn't like the added effort, but they're not paying the electricity bill, are they?
