The exercises that I feel has done most for my side delts are side laterals with cables and bands. I have done them in the following manner:
Attatch leather cuffs (the ones used on leg exercises) to the lower pulleys. Use the right side one on your left wrist and vice versa so the cables are crossed. Choose a weight you can use for about 15 controlled reps(1 sec up, 4 sec down) and do only 10-12 reps. Rest 30 sec. Repeat for a total of 4 sets. (4x training from Ironman Mag).
With bands do the same thing, but stand on the right hand band with your left foot and vice versa. Use bands that will barely allow you to reach ear level with your hands. Same speed as with cables.
It’s very important not to let the delts relax at the bottom position at any time. It will burn and it’s supposed to!
On a side note I find that 4x training is very effective on most bodyparts. It might not be the best for the ego due to lighter weights, but I could not care less as long as it produces the wanted results!
Give it a try, it’s well worth it.