NPC

I would suggest doing all your upper body one day, then lower body the next, then one day rest. Repeat.
Thats usually what I do, but I also pay close attention to how Im feeling. If your not getting a little tiny bit sore from working out an your resting 2 days, then your resting too much. You should only be resting if your too sore to workout, optimally you want like 36-40 hrs of rest after working peticular muscles. Unless your still sore, so a large part of the rest cycle seriously depends on how extreme your hitting your workouts. I had workouts at the gym where after I had finished and I had to wait 30mins to drive home because I couldnt control my arms yet.
Sometimes if you are a little sore a light work out will actually help relieve some soreness. Another general rule of thumb I use, if Im not getting a little sore after workouts then Im not working out hard enough because my body has adjusted to my current rountine so my routine needs to be altered.