Weight Training

Weight training is key to building muscle. The main factor to consider when planning your program is what exercises you're going to perform. Pick moves that work multiple muscle groups, as these build more mass, according to trainer Shannon Clark of Bodybuilding.com. A squat is more effective for muscle gain than a leg extension, for example. Once you've decided on your exercises and routine, you need a stimulus; you need to work hard enough to break the muscle down, causing it to regrow bigger and stronger. To ensure this happens, some form of progressive overload is required. Make your workouts tougher week to week by lifting heavier weights, performing more sets and reps or decreasing your rest periods.

Diet

Diet is as important as training when getting in shape for bodybuilding. Most bodybuilders will go through two stages of dieting. The first is bulking, which involves eating to gain muscle, and cutting, which happens pre-contest and is aimed toward losing as much fat as possible. You need an excess of calories to build muscle, according to coach Chris Martinez, but too many calories can make you gain fat, so aim to gain .5 to 1.5 pounds each week to ensure you're gaining lean muscle weight. When cutting, you need a calorie deficit, but too severe a deficit can lead to muscle loss, which isn't what you want. Nutritionist and bodybuilder Layne Norton recommends adjusting your calorie intake so you lose no more than 1.5 pounds per week -- any more could mean you're sacrificing muscle.

Cardio

Cardio isn't as important as weight training and diet, but it does still play a role. Burning more calories by adding cardio into your cutting routine allows you to eat a little more while still maintaining a caloric deficit, which can be extremely beneficial, according to strength coach and nutritionist Dr. John Berardi. If you exercise more and eat more, your metabolism increases and you build muscle and burn fat quicker than simply cutting calories through dieting, according to Berardi. Cardio is particularly useful when leading up to a competition as it aids calorie burn and fat loss.

Considerations

To build muscle, you also need adequate recovery between training sessions, so make sure you get enough good quality sleep and take at least two days rest between training muscle groups. Spend most of your year in a steady bulking phase, gaining muscle without adding too much body fat, but leave yourself three to four months to diet and cut down before a competition. If you're not gaining muscle when bulking, increase your calorie intake until you are; if you're struggling to lose body fat on a cut, lower your calories slightly, add extra cardio, or implement a combination of both.