The number of sets and reps you use depends entirely on what your goals are. For example, a football player would use an entirely different set and rep pattern than a bodybuilder would. Even bodybuilders use different set and rep ranges depending on what phase of their training they are in (pre-contest vs. strength/bulk phase).
Here are some guidelines to help you select the best set & rep range for you:
Strength/power: 1-5 reps (optimal strength range)
Strength and size: 6-8 reps
Size with some strength: 8-12 reps (optimal body-building range)
Local endurance with little strength or size: 13-20+
For bodybuilding purposes, it is beneficial to use ALL rep ranges, with emphasis on 8-12 reps. If you want to get really strong, plan on spending a substantial amount of time in the 3-5 rep range. If you want to get really big, spend a lot of time in the 6 - 10 rep range.
Load (amount of weight):
Strength/power: 85% or more of 1 rep max
Bodybuilding/Muscle mass: 70-75% of 1 rep max
See Calculating your one-rep max
It is well documented that maximal strength is increased by working somewhere between 85% and 100% of your one rep maximum. If you are working for muscle mass (bodybuilding) and not pure strength, your best bet is to use a variety of loads within the 70% - 95% range.
Volume (# of sets)
10-12 sets large muscle groups (back, chest etc)
6-9 sets small muscle groups (biceps, etc)
Training volume will vary greatly based on intensity of training and on the size of the muscle group. Large muscle groups like the back can handle 12 sets or sometimes even more. If you think about it, "Back" isn’t just one muscle like the bicep. The back is a group of muscles including the latissimus dorsi, rhomboids, teres minor and major, trapezius and spinal erectors. Because of the mass of muscles involved, you can do more sets without overtraining. A small muscle group like biceps is much more easily overtrained. 12-15 sets is just complete overkill for smaller muscles. If you’re doing that many sets, you’re probably not training hard enough (because if you were training hard enough, you’d be "smoked" by 8 or 9 sets.)
Frequency (days per week)
Train each muscle group with high intensity (to failure or just short of failure) once every 5 - 7 days. Whether it is once every 5 days or once every 7 days depends on your personal recuperative abilities. You be the judge - you know your body better than anyone.
Do not train with high intensity more than 2 days in a row unless you are genetically gifted with excellent recuperative abilities. Take the days off and allow yourself to GROW!
Day 1: Chest, biceps
Day 2: Back, abs
Day 3: Off (cardio only or complete rest)
Day 4: Shoulders, Triceps
Day 5: Quads, Hamstrings, calves
Day 6: Off (cardio only or complete rest)
Day 7:Repeat cycle
This split works each muscle group once every 6 days. The body part groupings are just a suggestion - you can combine them other ways, (back & biceps, etc) but try to pair one large muscle group and one small muscle group together.