Sit down on a flat bench or military bench and, with your arms fully extended, hold the dumbbells with your palms facing to the front. This is your starting position.
Raise one dumbbell all the way up as if you're trying to touch your shoulder with it. Then, lower it back down until your arm is almost fully extended (you should always keep tension in your biceps). Repeat entire movement for the desired or prescribed number of repetitions.
Perform this exercise in a smooth and fluid motion
Don't extended your arms completely when you lower the dumbbells down
SPECIAL NOTES & LEVEL of DIFFICULTY VARIATIONS
To increase the level of difficulty, slow down the movement or use heavier dumbbells.