If you are looking for extra shoulder development and strength, particularly in the front deltoid heads, but also in the sides, the military press is a no brainer.
The military press can be performed either standing or seated. Personally, I prefer standing as I find when the weights get heavier – particularly on a bench with no stable back rest – I have a tendency to wobble uneasily… but you should try both to find the one which suits you best.
Either way, the execution is the same…
Using an overhand grip outside of the shoulders, with the elbows and forearms tucked in and under the bar (preferably vertically) hold the barbell to the front of your body, level with, and resting lightly across the collarbone. Now, simply lift the bar straight upward and over head, locking your arms out, and then lower slowly.
It should be noted that some people may find the military press makes their shoulders sore in a not-so-good way, and may benefit from either adjusting their grip slightly, or by performing it with dumbbells instead. (Never continue with a technique which causes you pain – adjust at the earliest opportunity!)
The starting and ending positions for performing the military press with dumbbells is the same as the barbell variety… in fact everything is the same, but you have two options for hand positioning: Palms facing, or the way I prefer, palms pointing forward (just as if I were using a barbell.)
Of course, again, the benefit of using dumbbells means you are forced control each dumbbell independently, which can be very beneficial to muscle growth.