|Working with weights three times per week may be the most productive way to gain weight. Weight training provides the greatest amount of muscle growth for the energy expended without the risk of burning up all those extra calories you are consuming. Aerobic type exercises will just burn off those extra calories without much weight gain. Without any exercise, gained weight will tend to be fat - not muscle.|
You should lift hard and then recover until the next workout. Focus on the big exercises such as squats, deadlifts, bent-over rows, chin-ups, bench press and military press. These are the exercises that will turn those extra calories into muscle. You need the multiple-joint lifts that will shock your system and stimulate your body into growth. Focus on getting strong by adding a small amount of weight each workout. If you focus on strength, size will follow. If uncertain what to do, get help from a professional trainer, friend or someone at the gym with experience.