Diamond Stretch with autoasfixiation

This is a great masturbation technique that requires no equipment and, with care, it can be done discretely in your own bed.  In fact, I discovered this as a teenager still living at home.  Decades later, it still hold records for some of my best orgasms ever.
Make your hands into a diamond shape.

Place this diamond onto your mattress with your palms up and your thumbs pointing anteriorly (toward your head.  Lay face down on your mattress so that the top of the diamond (thumbs) is just under the head of your dick.  The tips of your fingers should be somewhere in the vicinity of your balls (or, if you'r disproportionately long, somewhere near the root of your dick.)  Masterbate by grinding into the mattress, stretching your dick by elongating the diamond, and ticking your balls.
Bury your face straight down into your pillow.  You will probably need to open your mouth wide to be able to breathe, but the key to this technique is that you want to have difficulty breathing.
The orgasm might approach more slowly than you're used to.  It will be like a distant rumble of thunder that you can hear approaching for a long time.
When you're ready, tighten your leg muscles, stretch the diamond, and tickle your balls.  This orgasm is different because it is caused in part by the lack of oxygen to your brain.  Don't worry, you can't kill yourself this way.  Just DON'T USE ANY EQUIPMENT, LIKE ROPES OR GAGS TO SUFFOCATE YOURSELF!

 (Just ask actor David Carradine...oh wait...you can't...'cause he died in the most embarrassing way imaginable!)
As soon as you're done, simply roll your head to the side and take in some deep breaths of fresh air...that will feel almost as good as the mind-blowing orgasm you just had.
The only reason I don't use this technique every time is that it is very difficult to watch porn at the same time, though I've had mild success by facing toward the foot of the bed and playing porn movies from my laptop, which is sitting on a chair near my head.

Important note about clean-up, especially if you're still living at home.  Position some extra cloth under your dick so that it can be picked up and tossed in the laundry.  If it's not thick enough, you will shoot your load into the fibers of the sheets and it will leave a very suspicious stain when mom cleans the sheets!  I recommend a t-shirt that regularly gets messy from sweat, so that it won't arouse suspicion in the laundry hamper.