Do external rotations. Attach an extra light rubber resistance tube to a stationary object. Grab the tube with your left hand and have your right side parallel with the tube. Your left elbow should be bent 90 degrees and be across your stomach. Now externally rotate your arm and pull the tube to the left. Do a series of reps, then turn the other way and do the other arm.
Do internal rotations. Now do the opposite of external rotations. Grab the tube with your right hand and have your right side parallel with it. Step to the left to get some resistance on the tube. Your arm should be extended out to the right and bent 90 degrees. Now internally rotate your arm and pull the tube to the left across your stomach. Do a series of reps, then turn the other way and do the other arm.
Do downward facing dogs. Come into a plank position. Now lift your hips up in the air and slowly push your weight back on your heels. Internally rotate your shoulder blades and hold for 30 to 60 seconds.
Do pronated arm raises. Let your arms rest at your sides with your palms facing in toward your thighs. Now lift your right arm out forward at about a 45-degree angle to your body and turn your thumb down. Lift your arm about halfway up and then lower it. Do a series of reps, then switch arms.
Use your bed. Lie facedown on your bed so your left arm is hanging off it. Grab a light dumbbell, bend your elbow 90 degrees and raise your hand up until it is even with your shoulder, then slowly lower it. Do a series of reps and switch sides.