The shoulder muscle, known as the deltoid, is what I believe to be one of the most important muscle groups to train when bodybuilding simply because well developed shoulders will make you appear wider and thus bigger – one of the key aims of bodybuilding.
To build all 3 heads of your shoulder muscles there are a variety of deltoid exercises you can perform which train the front, side and rear deltoid. The main compound movements such as the bench press and barbell curl will stimulate the front deltoid slightly while movements like the shoulder press will target the front and rear posterior deltoid.
The shoulder press is a compound movement which can be performed using 2 dumbbells whereby you hold each up level with your shoulders with your palms facing upward and then hoist them up and extend your arms in to the air directly above, and then lower back to the shoulder level. Not only will this exercise work your delts but it also hits your traps and your back slightly.
Isolation exercises are another great alternative for working your shoulder muscles as they target only your shoulders ensuring you fully stimulate them. I advocate using side lateral raises with dumbbells for this – you pick up the dumbbells in each hand and hang your arms by your side, then lift the dumbbells outward and upward with your elbows slightly bent until the weights are level with your shoulders and then slowly release them back down for a full repetition.
I recommend using a higher rep range when training your shoulders as they are a delicate muscle group and if you overload them too much you may face injury and shoulder pain at some point during your muscle building career, so make sure to start out easy with lower weight and high reps in the 10-12 range. The delts are similar in size to the biceps muscle therefore should be trained in a similar manner.