1. Bills. Make sure you are in agreement with your roomates about them - I had an issue with a roomate that maintained that he shouldn't pay more than 10 percent of the huge electricity bill because he didn't heat his room (not directly, I might add).
2. Choose an apartment with good insulation - this might not affect others as much as me (look the previous tip). But climate change and changing energy prices will soon this for everyone.
3. Start looking early and use your friends to find roomates.