Studies have shown that muscle tissue burns 9 times more calories than fat tissue. How cool is that! How can I build more muscle mass you ask? Resistance training is the most effective method of training to accomplish this. With that in mind, there are a few things to think about during your exercises in order to make your resistance training program more effective:
Concentric Contractions: Shortening of the muscle (good baseline indicator of muscular strength)
Eccentric Contractions: Elongating of the muscle (slow and controlled creates more micro-tears in the muscle allowing for more muscle rebuilding to take place resulting in an increase in muscle mass [AKA muscle hypertrophy])
Isometric Contractions: Sustaining a certain position for extended periods of time resulting in muscle fatigue. Isometric implies that you are resisting a force that is equal or greater to the force your muscles are exerting resulting in a stationary exercise. A good example of an exercise using isometric contractions is a plank.
In terms of building muscle mass, having slow and controlled eccentric contractions will be of great benefit to you. Try to hit each muscle group 2-3 times a week with a recovery period of at least 48 hours before repeating muscle groups. During your work out, exercising in sets of 1-3 with 8-12 repetitions would be appropriate.