Just about everyone in the gym wants shapely and muscular shoulders.  They help give your upper body that much desired V-taper, and they’re functional for sports.  Unfortunately, shoulder injuries are the most common types of injuries in the gym.  In this post I’ll go over how to develop your shoulders while avoiding those nasty injuries.  Some of my points are not well known, so be prepared to learn something new!

1. Strengthen your external rotators. This is the #1 key to balanced and healthy shoulders.  Most people in the gym work hard to develop their pecs and lats, which are strong internal rotators of the shoulder, while neglecting their rotator cuff muscles which are the external rotators.  As a result, the body can’t properly stabilize the shoulder joint during pressing exercises, and over time chronic shoulder problems develop.  The solution is to warm up and activate your rotator cuff before any upper body training.  You can find many good rotator cuff exercises on YouTube, but two of my favorites are face pulls with bands and standing external rotations (elbows positioned at your sides) with bands.  Pick one and do 2-3 sets of 15-20 reps without approaching failure.  The goal is to stimulate the external rotators and get blood into the area, not to annihilate the muscles.
2. Don’t overwork your front deltoids. The front delts get thoroughly worked any time you train your chest, and they work hard isometrically during bicep curls.  They’re also the primer mover in any type of overhead press.  It’s common for gym members to include 2 to 3 chest press variations on chest day and then come back a day or two later and do 2 to 3 shoulder press variations on shoulder day.  Then they wonder why they have shoulder problems.  One type of overhead press on shoulder day is plenty.  If you have shoulder pain when overhead pressing, and it persists even after experimenting with different wrist and elbow positions, don’t be afraid to drop the presses altogether and stick to various dumbbell raises and upright rows.
3. Avoid the known shoulder wreckers. I’m talking about narrow grip upright rows and behind the neck presses.  Both exercises put your shoulder joint in an unhealthy position and put you at risk for shoulder impingement.  Even if these exercises do not cause you immediate pain, for most people they will create wear and tear on the shoulder capsule and rotator cuff tendons and eventually wreck your shoulders.  There are better options out there, so don’t take the risk.
4. Use exercises with high deltoid activation.  EMG analysis and anecdotal evidence suggest that the greatest shoulder muscle activation occurs on the following exercises: dumbbell overhead press (front delt), wide grip dumbbell upright row (side delt), dumbbell lateral raise (side delt), and 45-degree bench lateral raise (rear delt).  If there are other movements that you feel strongly in your delts, great – include those in your routine.  However, you owe it to yourself to try out the four that I listed.
5. Do at least 8 reps per set.  You’ll maximize development by doing 8-20 reps per set and resting 30-90 seconds between sets.  A good working weight is 60-70% of your 1 rep max.  Leave the lower reps and longer rest periods to those who seek maximum power and are willing to take the risk that comes with maximal weights.
6. Use strict form.  Loose form, such as swinging the weights up on lateral raises and upright rows, not only increases chance of injury but encourages your traps to take over the movement.  There are better exercises for building the traps, so for the shoulders I recommend using strict form, slowing down the movement, and concentrating on using the delts.
7. Use a full range of motion on upper back exercises.  The rear delts are heavily involved in upper back exercises like pull-ups, pull-downs, and rows, especially during the last portion of the movement when your elbows are pulled back behind you. By performing those exercises with a full range of motion, you get extra rear delt work on back days and can potentially skip doing any direct rear delt exercises on shoulder day.  
8. Avoid upper body super sets and giants sets.  Super sets and giant sets consist of more than one exercise done with no rest in between.  They’re popular in CrossFit and occasionally used by bodybuilders to raise the intensity of the workout.  The problem with stringing together several upper body exercises is that the rotator cuff never gets a break during the sequence and can easily give out and cause an injury.  Advanced CrossFitters have extremely well-conditioned rotator cuffs that can handle the constant strain.  Chances are you do not.  If you want to do circuit style training, I recommend alternating upper and lower body exercises to give the rotator cuff a break.   

Sample shoulder workout

Warm up: face pulls – 3 sets of 15-20 reps, staying away from failure

Front delts: seated dumbbell overhead press – 5 sets of 8-12 reps

Side delts: wide grip dumbbell upright row – 5 sets of 8-12 reps

Side & rear delts: 45 degree incline bench lateral raise – 3 sets of 15-20 reps

Use a comfortable weight or band on the face pulls.   On everything else, use the heaviest weights you can handle for the target rep range while using strict form and resting 30-90 seconds between sets.

Good luck!