These are great if you can do them, all the techniques shown in articles never seemed to work for me however. One technique that I have learned is to do kegals as fast and hard as possible for a very long time.
I found this one night while in bed just after waking up in the middle of the night quite by accident. I'm not sure why I thought of doing kegals right at just that moment but, the longer I kept doing them, the better my cock felt. I just kept doing kegals when all of sudden I had one of those dry orgasm. It felt just like a regular orgasim with out cumming but, one than was far more intense and lasted far long that any orgasm I had ever had in my entire life. Although I did not ejaculate, afterwards I discovered almost my entire cock was coated with clear pre-cum that must have pulse out while doing so.
For me I need to be relaxed and it takes quite a while until my pelvic muscle can no longer hardly contract from being so pumped up from doing so many kegals. It is usually then or shortly there after that my dry orgasm starts. When they do, it just makes me kegal ever harder.
One I had about a month ago that was so unreal that it was almost scary as my orgasm just kept going and going and got more and more intense and lasted at least 3 minutes. After my orgasm had gone on for 2 minutes, I thought that is would never stop, and there was nothing I could do to stop it. That was thing that made it somewhat scary. The entire time it was so intense I had to yelled out loudly with every involuntary jerk of my rock hard cock. It reminded me of what it felt like to first have sex and was mind warping in intensity.
Maybe I was just really horny that night because after on a few minutes had passed, I started kegaling again and in short order had yet another intense dry orgasm that was just a long and slightly more intense as the first one had been. After only a short time in order to catch my breath, I did it more one time. The last time was not as intense not did it last as long as the first two, but did last for a full minute or just a little more. After that, I was totally exhausted from all the muscles of my body convulsing but, deeply wanted to kept this up.
I have not managed to have one these 3 in row dry orgasms since then but, have not really had the time to try.
I can't say this will work for everyone but, it worth a try. Please note, unless you regularly do a strong routine of kegal exercises as good penis health on daily basis, doing this make your pelvic muscle very, very sore. So be warned before hand.
Another source for learning some techniques can also be found at Multi-Orgasmic Man - Sol Sebastian. Not sure where I found this but, it is a complete course with 6 modules of both audio and video files. I however could never get any these to work for me however.
"Another is a PDF called "Multiple Male Orgasms - By B. Mat"