Rear Delt Fly
1. Bend at the waist so that your torso is at a roughly 30 degree angle to the ground. Allow your arms to hang straight down, palms facing each other in a neutral grip.
2. Move the dumbbells out and up in a wide arcing motion, stopping at shoulder height. Pull through your shoulders and don't use your back muscles.
3. Slowly return the dumbbells to the starting position
Note: This exercise looks very similar to the Back Fly. They key difference is that with the Back Fly, you want to use your back to move the weights, whereas with the Rear Delt Fly, you want to focus on the rear side of your shoulders.