Another Tri-Set Workout:
6 Front Shoulder Raises
6 Side Shoulder Raises
6 Rear Shoulder Raises
4 sets with 1 minute rest between sets
Don't lock your elbows for any of these exercises. Keep them bent and mentally tell your mind to concentrate on using only the shoulders to pick up the load. I personally prefer doing raises seated because it minimizes the use of momentum to bring up the weight. After all, the goal is to only use your shoulders.
If you want to challenge yourself more, do this large Tri-Set in under a minute. This will keep your heart rate up, which means you will burn more calories.