You need to be sure that you are eating the amount of calories needed to support your body type, metabolism, activity level, and weight goal.  For example I need 3,000 calories a day to maintain my weight of 155 pounds at my high activity level.  A week of averaging less than that amount of calories per day would cause me to lose weight.  I consume an average of 3,500 calories per day, 500 calories above my maintenance level,  when I am on a bulking (muscle-building) plan.

Read about the diet to build muscle. 

Drink 1 Gallon of Water Per Day! The best thing to drink is water, and a lot of it. Your body needs it desperately to perform well amidst the incredible strain you are placing on it with your workouts.

Water is crucial even for those who don't workout because your bodily functions (blood circulation, breathing, perspiration, digestion, etc) demand it greatly.

Drink at least .66 oz of water per pound of bodyweight every day.  A gallon of water a day is a good mark for most people, bigger people will need more. Water will excel your body in all performances. Hydration is king! Read the importance of water.

Split your water intake up over the course of the day.

Buy a Brita water pitcher – you definitely don't want to be drinking tainted tap water or expensive bottle water.

You will need at least 1 gram of protein per pound of bodyweight every day to build and maintain muscle.  Whey protein powder is superior to other protein powders because it the fastest-digesting and it has the best blend of amino acids that your body uses to build muscle.

No Protein = No Muscle Building. Without getting 1 gram of protein per pound of bodyweight every day, don't even bother weight training at all. You will not be giving your body what it needs to repair the muscles you have broken down if you don't meet your protein requirement every day. 

Weightlifting is a must when your goal is to build lean muscle.  Here are some rules to follow:

• Stick to free weights instead of machines.  Machines remove the negative motion of most exercises, which is highly necessary for effectively breaking down muscle.

• Use basic compound exercises primarily.  These are squats, deadlifts, bench press, bent-over rows, chin ups, lat pulldowns, and barbell curls.  Isolation exercises (flyes, concentration curls, leg curls, leg extensions, leg raises) are not important when it comes to bulking so stay away from them.

• Limit your workouts to 60 minutes of lifting. This means limit your actual lifting time to 60 minutes.  Overtraining is the main reason people don't see results from their weight-training programs. As a hardgainer, you will need to rest 3-5 minutes between sets.  So, you may be in the gym for up to 120 minutes total due to the lifting time plus the rest time.

• Use Heavy Weights, Limit Your Number of Sets, & Rest Properly Between Sets.  I recommend resting at least 3 minutes between heavy sets, which is what you should be doing on a bulking plan.  Sets should consist of no more than 8-10 reps; decrease the reps and increase the weight after each set of an exercise; if you can perform more reps than that, increase the weight. High reps are for fat loss and muscle endurance, the opposite of a bulking program.  You can only do one at once – bulking or cutting!

Workout hard, heavy and infrequently (no more than once a week per bodypart) on the big basic exercises, add weight to your exercises whenever possible, get enough rest & great nutrition, and you WILL build muscle!

Some of you will build a lot of muscle rapidly, and some of you will take a long time to add a measly five pounds. (It takes me, ALGetsBig, a long time to build muscle even with 3,300 calorie-a-day weeks.) That’s where genetics come into play. But you can maximize your potential as quickly as possible by following these rules.

Sleep 8 hours a night. Your muscles grow when you are resting, NOT when you are working out. You need to give your muscles enough rest and recuperation to allow the building process to take place. Work out no more than 4 times a week.

You need rest because each workout puts systemic stress on your entire body, no matter what muscle groups you are working. Your kidneys and other organs don’t understand or care that you are working different muscle groups each day. So, get out of the gym, get some rest, and grow!