The deltoids and the upper trapezius are what gives your shoulders the definition. Various weight training exercises will increase their size while strengthening the stabilizing muscles -- such as the rhomboids and rotator cuffs -- that lie deep to your shoulder joints and scapulae. Maximize muscle growth by performing three to four sets at 70 to 85 percent of your maximum exertion, suggests the National Academy of Sports Medicine. Lift at a rate of two seconds, and lower the weights for four seconds.

Shoulder Press

With a barbell, dumbbells or kettlebells, the shoulder press primarily works your deltoids while the middle and lower trapezius and supraspinatus assist in rotating the scapulae upward as you raise your arms. Sit at the edge of a bench and raise a dumbbell in each hand next to your ear with your elbows bent at 90 degrees. Exhale as you press the weights overhead until your arms are fully extended without shrugging your shoulders. Inhale as you lower the weights back to the starting position. To engage your core muscles more, perform the exercise in a standing position or perform the exercise with one weight instead of two.

Raises

Various types of raises emphasize different parts of your deltoids. The lateral raise, in which you lift your arms out to your sides to form a letter T with your body, works primarily your lateral deltoids. The front raises that involve lifting the weight in front of your body until your arms are raised slightly beyond your shoulder height works your anterior deltoids. In both raises, always keep your elbows slightly bent and avoid shrugging. All types of raises also work your trapezius and rotator cuffs.

Push and Pull

Pushing and pulling exercises, such as pushups, bench presses, pullups and standing cable rows, work your shoulders with other muscles in your torso and arms. If you want to burn more calories in your training session, perform one pushing exercise and one pulling exercises without rest between. This method, called a superset, allows one muscle group to work while the other group rests. In a study published in the April 2010 issue of "Journal of Strength and Conditioning Research," subjects who performed a superset workout had a higher metabolic rate than those who performed one exercise set at a time.