Stress your muscles - You don't have to kill yourself, but you must subject your body to out-of-the-ordinary stress each workout to grow muscle and to gain weight.
Be consistent - To gain weight and bulk up, you have to be willing to do whatever it takes, and work as hard as necessary and you have to be consistent. Your body responds to consistency. Sometimes it may get to the point of obsession, but it has to be that way for you to reach your goal.
Meals - Start eating six meals per day (space them out to about once every three hours). This is a weight gain diet used by those who know what they're doing.
Gaining mass- For mass, stick with compound free weight exercises like squats, deadlifts, bench presses, barbell rows, pull ups and bar dips.
Increase you water intake
Watch Brock Lesnar work out
