The other day, Faithful Reader PaulMmn left a comment asking how some guys manage those over-the-shoulder shots. I left a pretty short answer and it deserves to be expounded.
"And how do guys build up enough pressure for a 'fountain of youth' that launches far enough to paint the wallpaper behind their heads? I think I got in the wrong line that day! --PaulMmn"
Many years ago, before Men's Health magazine lost its way and began to focus on nutrition and exercise and advertising, it started as a 4-page, shrink-wrapped bulletin mailed out to subscribers. Those four pages were crammed with information for men about our most prized possessions: The cock and balls. How they worked, how they were supposed to work, what could (and did) go wrong. How to get more enjoyment out of sex and masturbation.
I learned more from those Bulletins than anything they've done since. That the cock is so much more than the sum of its parts.

Taking a trip back in time and pulling from my memory banks....
It begins with prolonged arousal, actually more than the edging I suggested in my response comment. Prolonged arousal means utilizing those frequent boners we get all day long. Tease them and coax them to hang around longer.
Kegels. Do those Kegels when you get hard.
You can do them and no one even has to know. It strengthens the pelvic floor muscles which can add power to an ejaculation.The Prostate can play a powerful role, too. Clenching your butt can add stimulation and help to build up the volume of fluid. The most intense ejaculations, the most pleasurable ones, are those where volume (buckets of cum) and velocity (forceful shooting) are combined. One of those early magazine issues hooked up with Cosmopolitan magazine for a survey. Women wanted to know more about what a guy likes during a blow job or hand job. Guys' overwhelming answer: Play with my balls. Fondle them. Lick them. Suck them. So, play with your balls.
The nipples, the inside of the thighs, are also a sensitive areas for men and can add to the pleasure and the building of the erotic pressure.
When you do get around to that jack-off session, take your time. Tease, play, stroke the boner. Flick the head, tease the Frenulum. Don't let all the luscious pre-cum go to waste.
Slap that boner on your belly or to the palm of your hand. Edge. Get right up to "the point of no return." And stop. Cool down a bit. then start again. 
Vary the strokes.
You could even do as Blogger Buddy at how2bate does. Stroke but don't cum. Build your ejaculation over days. When you do decide to let go, put those pelvic muscles and the prostate to use. Thrust your hips and squeeze the butt with the spasms.
That should have the jizz flying.
And leave you drenched and satisfied.
Happy weekend!