If you have not been exercising this portion of your body, it is wise to begin very slowly. Trying to perform perfect pushups (hands close together or farther apart) can not only injure your shoulders, you may also over stretch your serratus anterior and possibly cause problems for other scapular stabilizers.

An easy exercise to do that will totally target your triceps without compensation of other muscles, is to 1) lay on your back, hold a weight in your hand (5# to begin would be great), keeping your elbow straight-point your fist toward the ceiling. This is your starting position. Carefully (so that you don't give yourself a head injury , bend only your elbow so that the weight is slowly lowered by your ear. Do not move your shoulder from the start position. Then extend your elbow back to the start position.

The key is to perform several sets of 10 to 15 repetitions...slowly and controlled. Build to about 4-5 sets and then drop down to doing 1-2 sets however add 1 pound. Good luck!