Pick a couple of dumbbells and stand with a straight torso and the dumbbells on front of your thighs at arms length with the palms of the hand facing each other using a hammer grip.
While maintaining the torso stationary (no swinging), lift the left dumbbell to the front with a slight bend on the elbow. Continue to go up until you arm is slightly above parallel to the floor.
Now lower the dumbbell back down slowly to the starting position as you simultaneously lift the right dumbbell.
Variations: This exercise can also be performed both arms at the same time. Also, you could use a barbell as well.