Overhead barbell and dumbell presses. Compound movements always add the most size. For side delts, try lateral raises and upright rows which will also hit the rear delts.
I have been seeing great improvements in size and strength over the last few weeks by doing strict BB military press for warmups, heavy push-presses for work sets, immediately followed by 2 sets of seated DB presses.
I GOT IT! Arnold Presses. Nothing better. When i do these i feel it sooo much in my front and side delts its not even funny. I have to use lighter weight on laterals and upright rows after 4 heavy sets of these.