Oddly enough I just stumbled across an article about this…
I take it you're asking about how to 'shoot' your ejaulations and not about how simply to ejaculate.
The volume of ejaculate, or 'cum', and the ability to project it some distance rather than have it drip out of your penis, is largely down to your natural ability. But if you aren't naturally gifted in this sense, do not give up hope, there are some things that can be attempted.
Firstly, abstaining from sexual activity will increase the amount of ejaculate.
Secondly, you should train your pelvic floor (PC) muscles by doing kegels. To locate the muscles, stop mid-stream whilst urinating. The muscle you used to stop the flow of urine is your PC muscle. To exercise it, slowly but firmly contract that muscle, hold for a count of 3, and release. You should start slow, but work your way up at a comfortable rate.
When you cum, you'll notice your penis contracts several times. Doing kegels will make these contractions more intense, and if you're lucky the semen will shoot rather than drip.
(Note - do NOT hold a kegel as you are about to cum, this will attempt to prevent ejaculation rather than let it happen more smoothly).
Third, the more sexually turned on you are, the more intense your ejaculation will be. A common technique is to masturbate until just before the point of ejaculation, and the to hold it back and wait until the excitement subsides. And then repeat, and again stop before you cum. Do this several times, the more the better. Finally when you're ready, go all the way and don't stop, when you cum you will most likely have multiple cumshots and cum quite a bit more than normal.
This is because as you build up the excitement, the more sexually turned on you are, the more watery your semen becomes. Because it's thinner than usual, and there's more of it than usual (as doing this builds up ejaculate), you will more than likely shoot the cum.
Practice makes perfect, and welcome to the cumshot club. You'll need to turn in your cumdrip membership to join
Read more: hxxp://wiki.answers.com/Q/How_do_you_have_a_cumshot#ixzz18UUXTQHI
I guess I am lucky that I'm gifted with the ability to have quite powerful ejaculation. If I want to shoot really far, then I do it basically as you wrote, don't masturbate for a few days and hold myself on the edge of orgasm for as long as possible.