The deltoid muscles -- delts -- form a small muscle group comprised of three heads: the anterior or front; the medial or side; and the posterior or rear delts. Building your delts can be a challenge, because they are small muscles and fatigue quickly when involved in your chest workouts. Focusing on two basic movements along with isolating -- performing single-joint movements -- to hit each head of the deltoid will build your muscles.
Perform a clean and press exercise. This is multi-joint movement involving your legs in the beginning and finishing with shoulder isolation. Start with the barbell on the floor, squat to pick it up then stand erect with your arms hanging down naturally. Bend your knees, then shrug your shoulders, extend your legs and pull the barbell up to your shoulders. Dip your knees again -- thrusting one leg forward and the other back to form a split stance -- to help you control the barbell in front of your upper chest, with your palms facing forward. Push up through your legs, extend your arms and press the barbell overhead, pause, and then lower the barbell back to shoulder height. Return the barbell back to the floor and repeat.
Work your lateral deltoids by doing lateral raises. Hold a pair of dumbbells in your hands with your palms facing your legs. Raise the dumbbells to shoulder height, keeping your arms roughly parallel with the floor, with your elbows slightly higher than your wrists. Lower the weights under control to the starting position.
Use a straight or EZ curl bar to do upright rows. Grasp the bar with your hands shoulder-width apart or slightly narrower. Pull the bar to your neck, keeping your chest raised forward. Lead this movement with your elbows and keep your wrists lower than your shoulders. Raising your wrists to elbow height shifts the stress of the exercise away from your delts. Lower the bar slowly and repeat.
Perform rear delt rows on a Smith machine. Stand near the machine with the bar low to the ground. Bend from the hips while keeping your back straight over the bar. Clasp the bar in your hands and raise it to your upper chest level. Keep your arms perpendicular to the bar. Straighten your arms and repeat.
To build your shoulders, perform six to 12 repetitions and three to four sets per exercise. Use sufficient weight so your final reps in each set are challenging.