This is one of my favorite shoulder workouts. It combines heavy compound movements and lighter, isolation exercises to build your shoulders to the absolute max. I even used this workout to get ready for the 2014 Mr. Universe competition. It's quick, brutal, and great for hypertrophy.
If you are the type of lifter who always wants to try something different, this is an excellent workout to mix into your rotation. Each exercise targets a different part of the deltoid: The presses primarily target the front delts, the upright rows target your traps and medial delt, and you finish by flying in to blow up your posterior delts.
Get your body and mind ready for this deltoid demolition. With all the sets, reps, and triple dropsets, your gym will look like a dumbbell graveyard.
A longer rest period may provide more maximal strength, but if I wait too long, I get cagey. I don't like waiting more than 60 seconds.
The first two sets of behind-the-neck presses should be performed with light weight to warm up your shoulder joint and push some blood into your delts.
Shoot for 8-12 reps, but if you can lift more, go ahead. Training is often instinctive. It's not always a "by-the-book" sort of thing.
With 3-4 working sets on an exercise, I like to get warm, go heavy, go heavier, and then lighten the load on my final set.
If you're ever performing a really heavy or max-effort set, it's good to get a spotter. If you can't handle the load, you need someone to help you bail it.
Dropsets are more art than science. They require some feel. Use your intuition to know when to stop. I don't like to stop if I can keep lifting.
I wear headphones so people don't bother me, but I don't listen to gym music. Listen to whatever tunes help you focus on the task at hand. It doesn't matter if it's country or heavy metal.
If you get gassed, finish a set with partials. Get something from every rep! Don't give up on yourself.