What Are Some Good Exercises for My Deltoids (Shoulders)?

Your deltoids are the muscles that make up your shoulders. You have three deltoids: anterior (front), posterior (rear), and medial (lateral, middle). Although large shoulders are often associated with a strong physique, your deltoids are relatively weak compared to many of the other muscles in your body. Your deltoids are designed mostly for assisting other muscles, not doing the bulk of the work. Targeting your deltoids often requires you to perform compound movements that incorporate them.

Dumbbell Shoulder Press

The dumbbell shoulder press is one of the best exercises you can do to hit your deltoids. They work your anterior, medial and posterior delts. When doing this exercise specifically to target your deltoids, I recommend using a lighter weight than what you can actually shoulder press. The reason being that if you lift your max when you shoulder press, your arms will take over for most of the work, but if you lift light, you'll get better results in your delts.

Pushups

I know, you're thinking, "but pushups are a chest exercise." Yes, they are, but remember what I said: Targeting your deltoids often requires you to perform compound movements that incorporate them. Although pushups are predominately a chest exercise, they're a great exercise for working your anterior deltoids. Elevated pushups (feet on a bench) are even better for targeting your anterior deltoids. If you really want to challenge your anterior delts, position your hands near your waist while you do pushups. This is known as a "pseudo planche pushup" and it's a killer shoulder workout.

Lateral Raises

You've probably seen people doing this exercise at the gym a lot. This is a great one for targeting your medial (lateral) deltoids (go figure). I also recommend using a light weight when doing lateral raises, because they're virtually impossible to do with a heavy weight. All you do is stand up with your feet shoulder-width apart and a dumbbell in each hand, then lift the dumbbells laterally until they are parallel to your shoulders.

Bent Over Lateral Raises

This exercise is exactly the same as doing a lateral raise except you bend over at the waist 90-degrees and keep your back straight. The reason you want to do bent over lateral raises and lateral raises is because bent over lateral raises will place a strong emphasis on your posterior deltoids, while lateral raises will mostly just hit your medial delts.

Sources:

http://www.ironworkout.com/shoulder_workout.htm

http://worldfitnessnetwork.com/deltoid-shoulder-muscle/