For resistance training programs, your rep range will depend on your goals. The more muscle you want to gain from your program the lower your rep range should be. The basis of any resistance training program, should be between 4-20 repetitions to failure. If your goal is just muscle gain, you need to stimulate type II B muscle tissue. This type of muscle tissue operates purely off of stored energy and is the primary type used for low rep range, heavy lifting, to failure. 4-12 repetitions to failure is ideal for this type of program consisting of three to four exercises per muscle group and two muscle groups per workout (such as chest and tris, back and bis, and legs and shoulders).
If your goal is simply leanness with some strength gains, then higher rep range workouts are ideal. By working higher rep range, your focus will be type II A muscle fiber which is primarily used during 12-20 rep range. Typical structure for this type of program is full body with one exerscise per muscle groups. The rep range for this type of program is 12-20 reps.
Then, of course, there is the in between semi-split workout. This workout structure would entail three muscle groups per workout (chest, shoulders, and tris; Legs, back, and bis) and 4-20 repetitions per exercise depend on you primary goal. go for low rep range for muscle gain, a mix for a little bit of everything, or high rep range for basic strength gains and leanness.
The beauty of working out is you are free to change things up for flavor. Feel free to change your workout structure and rep range to keep your workouts fresh.