Hold a tin of beans or bag of sugar, or if you have them weights( smallest weight start) in each hand.
With one arm lift it slowly out so your arm is straight, then bending your elbow put your hand behind your head.
Don't lock your elbow.
Straighten your arm slowly and repeat 5 times.
Then do the same with your other arm.
Another one is with the keeping your arms at your side , with a weight in each hand.
Palms facing inwards and as you bend your elbow lift and turn your palm so it's facing upwards, hold your elbow bent, and close to your body for a count of 4 and then slowly put your arms down.
Do this for 5 times.
Each day if you do this you'll notice a difference.
I know this because I'm have personal trainer at the Gym and he showed me how to do this on Thursday.