See bold above: Great advice. Way too many people treat laterals like fluff movements. They do high reps, use light weight, go for the burn, etc. That's all bullshit. If someone wants to build truly monstrous delts the ONLY way that is going to happen is if they treat their side and rear laterals like they were a major compound lift, such as squats, bench presses, or deadlifts.
A bodybuilder must get enormously strong on side and rear laterals in order to build maximum size. There is no way around it. We wouldn't do only light pump sets to train chest, back or legs, so why should we treat the side and rear delts like they are any different?
Strength is relative, but progressive resistance should form the foundation of side and rear delt work, just like it does for our larger muscle groups.
The only difference between laterals and other mass-building movements is that I believe the reps should be a little higher for best results. While 6-8 reps may be fine for some upper-body muscles, I have found that side and rear delts respond best to sets of 8-15...and sometimes even as high as 20. However, these sets should be gut-bustingly hard sets to failure or damn close to it.