I usually do side laterals with the cables. The resistance is constant throughout the entire ROM whereas with DB's, the resistance dies as you lower the weight.
Also, a slight twist of the wrist as you reach the apex is great for achieveing a maximal delt contraction.
My opinion on this is that basically everyone is somewhat different biomechanically. Experiment around and see which methods tweak your delts the best. I've found that using cables, bringing the handle in front of me, going a bit above parallel, and twisting the wrist at the top are the best ways to go for me. Also, I bend over a tad and bring the cable handle in a slight backward arch instead of straight out to my side.
This one of the exercises that you've just got to find the right groove and perform it strictly for it to be benefitial.