There are three strengthening exercise which can be done at home or at the gym . these three exercise seem to help with strengthen and build muscles around your upper shoulder, rotators cuff and posterior of the neck. for each exercise make sure to keep your knees slightly bent and use a can soup or light weight under 5 pound to start and get use to the posture and movements. repeat 6-12 reputation and 2-3 sets for exercises 2-3 times a week.
 

SHRUGS
Hold arms at sides, palms facing in. Keeping arms straight, pull shoulders up to ears, pause for a second, and lower. Make sure perform the movement slow.

2. REVERSE FLIES
Bend forward so chest faces floor, arms hanging down, palms in. With elbows slightly bent, squeeze shoulder blades and raise arms to sides, parallel to floor; pause, then lower.( be careful not to hyper extend your neck) keep it in the neutral position.

3. UPRIGHT ROW
Start with palms in front of thighs and facing legs. Bend elbows out to sides, and pull weights up to about collarbone level. Pause, then lower.  perform this exercise slow and make sure you pause when you have the weigh up close to your chest.