I first learned about extreme stretching from John Parillo back in the mid-eighties.It has stood the test of time.John's idea was that muscle growth is inhibited by the constriction of muscle fascia.
Basic Facts About Fascia

Fascia is a fibrous membrane that envelops, supports and separates bundles of muscle fibres.

Fascia transmits the energy of muscle action to the tendon and bone.

Fascia maintains the structural integrity of muscle fibres

Muscle fascia is targeted for lengthening during flexibility stretches.

He felt that if you could stretch the fascia when the muscle was "pumped",it would make room for new growth.He also did something he called "muscle planing"which was basically "extreme massage"when the muscle was pumped.He claimed he could add 1/4" to your biceps in 10 minutes with this.He also sold Mct oil as a supplement,so maybe he knew another use for it.Be that as it may...

The idea,as I said is to extreme stretch the muscle after a set.I think this works by inducing micro-trauma,just as the negative portion of the rep does.The positive portion,of course,setting it up.I emphasize the negative portion,but I don't advocate negatives only in a set.I think this "micro-trauma is the stimulis for the hypertrophy response.I read a study once where they attached a weight to a birds leg and stretched it for 8 weeks.The stretched leg was considerably larger and more muscular than the other one.(Pretty messed up for the bird,after all that)

Regardless of how,this does work.I've used it mostly on my calves,chest and back(cause they're easier to stretch,probably)and it really has made a big difference.Okay,after you're warmed up of course,you want to REALLY stretch the target muscle,after a set(or sets),Here are a few examples-

Chest-Lie on a bench with a couple of heavy DBs.Keep your shoulders in tight,and your elbows well bent.Go into the bottom position of a flie.Hold for 60 sec.Breathe into the strech,and with each breath,let it sink a little lower.Do this for 4 weeks and come back and tell me how much fuller your chest is.

Back-You could hang from a chinning bar for 60 sec.Use straps if you want and also attach a DB around your waist if you want.You could do the thing where you bend over and grab a support and twist your body away from the side you're stretching.

Shoulders-John advocated "skin-the cats".This is where you hang from a chinning bar.Lift your feet up to the bar,and let them drop down in front of your body.This is going to rotate your body so you're hanging with your arms behind you.This is very effective but it may not be a good idea for those with shoulder problems,and that's probably most of us.You can do a less extreme variation of the same thing by setting a bar at shoulder height on the squat rack.Facing away from the rack,with your hands palms down on the bar,walk away from the bar and bend your knees to achieve a stretch that is tolerable to you.

Biceps- Do the same thing as for shoulders,but with palms facing up.

Triceps-Hold a heavy DB behind your head and let it hang.

I think you get the idea.If anyone doesn't know a way to stretch a particular body part,feel free to ask.If you can't feel a stretch,play with your body position until you can.Ask yourself,"What do I need to do,to feel this?"Sometimes a simple shift can make a big difference so experiment.I ALWAYS strech my calves after each set,and I always have the best calves in any gym I train in,so...