Arnold developed his own deltoid exercise to hit the front and side heads…
Arnold always included this exercise in his shoulder routine and claimed it was the very best deltoid exercise he knew of, because of the tremendous range of motion it afforded him. They are called Arnold Presses.
How to perform the Arnold Presses:
Standing, with the elbows to the side of the body, a dumbbell in each hand, hold the weight at the shoulders, with the palms turned towards you. (Note: Elbow positioning should mean the palms aren’t fully turned towards you, but almost.)
Now, using a smooth and controlled motion, press the weights up whilst simultaneously twisting the palms so they face forward by the time they are rising above the head. You shouldn’t lock the arms out, but stop the press in a position slightly short with the elbows still bent. That way, all of the stress is kept on the deltoid muscles rather than the bone structure.
Simply reverse the same movement path on the way down.
Arnold describes his exercise as a cross between a Lateral Raise and Dumbbell Press.