How to do the Arnold Press Shoulder Exercise:
Starting position: Bottom of the movement - grasp two dumbbells, palms face inward (towards your body) and elbows more or less at your sides.
Top of the movement - as you press the dumbbells upward, slowly rotate your hands and arms so that your palms face outwards (away from your body) during the mid range of the movement.
Top of the movement, you are in the same position as a regular dumbbell deltoid press. You may first want to try the dumbbell deltoid press, as well as a varition of it: hammer shoulder press with dumbbells. They are both easier to do before attempting this exercise plus it will strengthen your shoulder muscles for this exercise Also, do not lock your arms at the top of the movement.
Now lower the weights slowly back to the starting position and repeat for desired reps.
Breathing is very important when weight training. Breathe out as you raise the dumbbells and breathe in as you lower.
Do 4 sets of 12 repetitions.