Here is a video that shows several variations of the scapular pushup used to improve scapular stabilization by training the serratus anterior muscle.
These exercises progress through more and more difficult variations as the subject gains strength.
In golf, as in any other sport, increased strength, endurance and flexibility will help to minimize the chance for an injury.
Weakness in or injury to the muscles of the rotator cuff is one of the most common problems for golfers.
This video demonstrates a rotator cuff strengthening exercise routine for the golfer.
The video shows an external rotation exercise with a dumbell. Strength training is accomplished by finding a weight with which you can do two sets of 6 to 8 repetitions each. As you progress from there you would increase the weight after you can do 3 sets of 15 reps.
The mechanics of the exercise are just as important as the weight - you'll find this to be a common theme for all exercises of the rotator cuff.
Check out this page for a shoulder stretch specific to the golfer.