It varies quite a lot. A quick wank just cause I'm getting desperate and it mostly just dribbles, more typically I'll shoot 1-3 ropes about to my belly button, then dribble the rest, and if I'm super-horny and edging hard, I often shoot most of it in big spurts up to my nipples - or once in a blue moon, my face. It also tends to be runnier, and there's more of it, and the orgasm lasts longer or comes in waves.
The things that make the most difference are edging (or with a partner, foreplay and then going slow and swapping round when I'm getting close), general level of excitement (watching something really hot vs. half-assed lazy wank) and waiting till after I start leaking precum before blowing my wad (lubricates the pipes?).