The principle of progressive resistance exercise is that as you get stronger you need to progressively increase the resistance in order to gain strength and muscle. You can start out doing ten repetitions with a given weight but then increase the weight and do five more repititions.You exercise routine should be designed so that fatigue does not limit your lifting ability. You should only work one set of muscles at a time then move to a different group of muscles. The resting muscles will repair themselves and grow larger. The muscle group need to recuperate.
If your goal is to gain large amount of muscle you can try the bulk up method. You can do three to five sets of lifting on the large muscle groups. Start out with heavier weight but it should not be something you cannot lift safely. You should work up to eight to ten repetitions and this will take a few months. After you reach ten repetitions you can increase the weight. Once you have achieved this level you can use lighter weights and increase the speed of the movement. Once you have reached your desired weight you can maintain these exercises to keep your shape and muscle tone.