depends on what you are working for. a personal trainer gave this guide when throwing together a weight training routine on my own
Muscular Endurance: 15-20 reps, 3 sets, 3 x per week for 6 weeks or more
Muscular Hypertrophy (size): 10-12 reps, 5-6 sets, 3 x per week for 12 weeks or more
Muscular Strength: 4-8 reps, 3 sets, 3 x per week for 12 weeks or more
Muscular Toning*: 12-15 reps, 3 sets, 3 x per week for 6 weeks or more
kassia
When they discover the center of the universe, a lot of people will be
disappointed to discover they are not it -- Bernard Bailey