I work on a kind of a rotating schedule.
M - Chest / Tri's
T - Back / Bi's
W - Off
Th - Shoulders / Legs
F - Chest Tri's
S / S - Off
M - Back / Bi's
T - Shoulders / Legs
W - off
Th - Chest / Tri's
F - Back / Bi's
ect....ect.. ect..
So basically every body part gets hit once per week and every third week it gets hit twice in a week (just to shake things up)... I do this on and off, I only vary the intensity (weight, reps, supersets, ect)..