Well, you can sleep on your back, side and stomach. When you are farther along, you should sleep on your sides. I found it most comfortable to have a pillow under my belly and in between my knees (a body pillow worked great), and then one behind my back for support. If you still can't sleep, you could probably get a sleep aid, talk to your doctor.
Depends on how far along you are. If you dont have a huge belly yet, you can sleep any way that is comfortable for you. Your body will tell you if you need to move. If you do have a huge belly, its really hard to sleep in any position, but its the same...how ever you can get comfortable!