The most important thing to consider when choosing rep and set amounts is that in order to see muscular improvement you should work to fatigue. This can be described by the term momentary muscular fatigue, the inability to perform one more repetition of an exercise. Therefore, if you increase the weight you are lifting, closer to your maximum, it will require fewer repetitions to accomplish your goals. This can be an important time saving measure. Reps and Sets Reps are the number of times you lift the weight.
Sets are a specific number of repetitions grouped together.
A warm-up is important. This is to warm-up your muscles and prepare them for exercise. This should not be overlooked because it will reduce your risk of injury. It is comprised of both a general warm-up, jogging or walking, as well as a few reps of light weights working the muscles you will be training. A cool-down is also necessary.