I’ve been doing a routine and wonder how many sets you should do I always believe in 3 or 4 sets.  In some cases 5 sets can be good if you lower the reps.  Switching your number of sets sometimes can help shock your muscles to grow or get stronger.  For endurance I would go with 4 sets and higher reps.  For just mass 4 set maybe 5 for lower reps.  Occassionally you can do some different like 2 sets of 30.