I'm surprised the following "methods" haven't been mentioned at all. Get some SKILLZ dudes, this shit helps with whacking AND with fucking!
1. Squeeze with your hand.
Squeeze the urethra very very tightly, utterly closed, with your hand when you start to feel yourself nearing (or going beyond) the "point of no return." By cramping down EXTREMELY hard with your hand on the point immediately above your corpus cavernosum (erectile tissue: the part that is hard like a girder, within the inside of your penis) but still below the edge of the glans (head: it does get puffier, but the glans has no "hard structure" on its inside even when the rest of the penis is fully erect), you can effectively close off the entire urethral canal. Doing so can "force" your body to fail to cum because there's no outlet for the stream of semen.
I find that the required grip is best effected by thumb and a larger finger, either index or second ("shoot the bird") finger. I mash the ball of the last section of my thumb hard against the inner crease of the first joint of the finger, with the dick in between the two.
Though it doesn't take very much training or practice to figure out this technique, nevertheless it can go mildly wrong. Nothing major, no surgery or pain or anything, but it might not prevent the cum. For example, if done slightly too weakly, or otherwise in a manner that fails to prevent your your ejaculation muscles from entering into their orgasm-inducing peristaltic waves, then you may experience those waves, thus unfortunately "ending" your session since most of your body thinks you have cum, but you will not experience the enjoyment which those waves usually induce. Enjoyment of orgasm comes (mostly) from the inner sensation, within your urethra, of the fact of liquid (your semen) zooming past sensors that are roughly at the edge of the glans. This sensory location is exactly the point which, by this squeezing technique, you are deliberately constricting, thereby (you hope) preventing it from sensing the zooming liquid. In fact, you're stopping the flow of the zooming liquid.
So, it's possible to do it poorly. You can end up with half an ejaculation, some drizzling cum, and also no sensation of orgasm, while also failing to prevent the actual act of peristaltic waves which signal your body to enter post-orgasmic refactory period. Thus, you didn't feel like you did cum, though your body will act like you did cum, and your "edge" has been "wasted." Some folk like this, and call it a "ruined orgasm." I guess it's one sort of tease, but it won't help you on the topic of this thread, which is "edging without cumming." Instead, that would be "edging WITH cumming but not enjoying it as much as usual."
But you can beat this disadvantage by doing a better job of constricting, by moving the constriction-point farther up (away from the tip, toward the body) your penis shaft, by accomplishing "full" constriction, by monitoring your own internal sensations better such that you can coordinate the "point of no return" and the fingers, etc..
2. Squeeze with your PC muscles.
Do Kegels. Lots and lots of Kegels. Exercise the PC muscles. There are different sets of sphincters in your body, some of which feel like (from the inside) they work to stop the flow of urine. Work those muscles out. GIT POMPED BAY BEE.
As you gain control and strength in your PC muscles, you'll find that there's a point at which your PC muscles develop an adequate level of strength to "overcome" your ejaculation. So, when you near the "point of no return," you just tighten your "grip" (mentally, by constricting your PC muscles) on the penile sphincter (the sentence is written as though we had a penile sphincter, but we don't; nevertheless, proceed as though we do) in much the same way that your hand would do in method number 1., above. You are not ACTUALLY both (a) ejaculating by means of one set of muscles farther up and inside the body, while simultaneously (b) preventing the ejaculation stream from exiting your penis by means of a second set of muscles farther out and down the length of the shaft. The flow doesn't "start" back up in the inside but "get stopped" way out at the tip. But that's kind of what it FEELS like you're doing.
In fact, I personally find that this act of "holding back" with the PC muscles doesn't exactly stop ejaculation, as much as it stops arrival at the "point of no return." It essentially "pulls down" on the inner growth of nearer-and-near-to-orgasm feeling, or "sucks back" on that sensation, dragging it backwards along the length of the penis shaft. That's just a metaphorical expression of the sensation.
Another way to put it, is simply to say, "over flex." Just flex the HELL out of your dick while pumping it. Flex so hard that the PC muscles "cramp" backwards inwards whateverwards in on themselves. This results (for me, at least) in a loss of arousal and a decrease in the overall erection level of the penis, plus a back-down from the near-cum feeling. Time it right, and this is another useful technique for stopping an almost-cum.
3. Stroke the blood down and out.
Use your finger or a knuckle of your thumb to "reverse" the liquid flow that seems to be building up within your urethra on the underside of your erect penis. Just "mush" the "liquid" (it isn't there, but your urethra feels like it's full of liquid because its walls have engorged and therefore enlarged and stiffened, just like your erectile tissue has engorged) back upwards (away from the tip, toward the body) and inwards. Grab hold of the dick and feed or push or snake the liquid that's "in the urethra" backwards toward your body.
Done a little bit more elaborately, it's possible to even reduce the whole erection, not just the urethral swelling, with this technique. Simply "push back" the blood that is within all of your penis -- not just the urethral walls -- in such a way that your erection gets reduced. Mush it on this side with one finger, that side with another finger, etc.. By "reverse engineering" the flow of blood which caused the erection, you can manage to un-cause that erection. This technique is a bit tricky because if you do it too gently, or with too generally orifice-like a grip, your penis will fail to "lose" the blood that you're pushing backwards toward the body. Instead, it will get a sensation that resembles entry into an orifice, and that will be positive toward orgasm, rather than negative and away from orgasm. So, make sure you aren't making a "ring" that feels good, when you push the blood backwards. But it isn't difficult to figure out how to feed blood out with your hand, without also mimicking a vagina (or mouth, or anus ...).
4. Change body position.
If I'm in a squat, or half-squat, and I flex my thighs HARD to hold up my weight and even flex them harder than that, this type of pressure in my leg muscles will "drive" an orgasmic sensation into my penis. I can kind-of accomplish the same "drive" by means of my biceps, my trapezius muscles, and other parts of my body. A "hard flex" anywhere will "zing" my dick a little bit.
So, do the opposite. Instead of squatting in a half-tuck, straighten out and relax all the leg muscles. Instead of holding the elbows at a 50/50 bend, straighten your arms (but don't flex the triceps hard!), and raise them at the shoulder. All build-up of lactic acid is a bit of an orgasm driver or intensifier. Get yourself to the point of controlling your body by reducing rather than increasing lactic acid. It is, after all, a simple bodily response, much like when the doctor whacks your knee with that little red rubber mallet. Learn which positions direct or redirect or enable or disable which responses, then implement accordingly.
5. Pull on the balls.
Your testicles retract into your body when you cum. You cannot cum if your testicles are not adequately retracted. Do not let your testicles retract, and you will not cum.
It's a bit of a trick to figure out just how to "pull" but you don't really miss the concept once you've given it a try. I find that a groomed scrotum and root help out, and using lube (not only on the shaft) on the scrotum, testicles, all over the place, is useful. I use one hand to whack, the other to REALLY pull the balls down. Down like six inches, man, way down. Don't let your scrotum start to "shrivel up" into its pre-orgasmic position. Just keep your balls way down low the whole time.
The grip in the hand which is pulling on the balls must (a) make sure to get both testicles, not just one or the other, and get them as far away from the body as possible; and (b) crimp the inside ducts and pipes and shafts 'n' stuff.
Just as with techniques 1. and 2., above, the crimping or "stopping off" of tubes seems to be helpful here. I don't actually think that the tubes from testicles up into body are operative during orgasm, since the supply of ejaculate and semen, part of which the testicles do (of course) produce, has already been tapped well before tonight's little anti-orgasmic episode, so the sperm produced in the testicles can't be "prevented" from getting to their eventual target merely by blocking off the testicles' outlets at the last possible moment. Nevertheless, that's what it FEELS like. Grab hold of the balls, pull 'em down, way down, and block off the internal flow from balls up to body. Squeeze on that dangling sack, man, SQUEEZE hard.
Don't squeeze ON the balls, but squeeze ABOVE them on the whole strap of skin that's now stretched from dick-shaft downwards. You can, I guess, pull to the side or, if you're creative, pull to the side and around and then up, even, why not? But the idea is to get the testicles into the bottom of the scrotum, and then to lengthen the scrotum and continue to prevent it from shortening on its own. Put a rubber-band on it if ya gotta! Not that I've ever tried that ...
6. Combine the above techniques with deep relaxation.
You may not have noticed it, but when you're nearer to orgasm you lose control of your other body functions as autonomous systems take greater control. Your hand can "move on its own," for example. Your breathing speeds up. Your muscles all over the rest of your body flex (and "drive" you to orgasm, see number 4. above).
So, reduce your breathing. Lots. Deep breathe (without holding your breath at all, always flowing in and out, never stanching the flow). Deeeeeeep brreeeaaattthhhe ... deeeeeeeeeep.
In fact, I find that simply filling my lungs with a big ol' "sigh" or "yawn" will almost inevitably prevent orgasm.
Well, that's some suggestions. Love to hear more.