The most important thing I find that is in your control with regards to your snap shooting technique is constancy. Get to know where you naturally hold your marker. For me personally my barrel is lined up with my nose, regardless of which hand I'm shooting from. With enough practice and repetitions of shooting with my pump and barrel held in the same position I have a built up expectation of where my paint should land when I pull that trigger, assuming my barrel is clean and my paint isn't dimpled. If my snap is off, instead of moving my gun to correct the shot I'll make micro-adjustments of my torso to orient my head/body/pump to make the shot. I hope that makes sense to you. The next time you are at your field just shoot through a whole pod of paint to get a feel for where your point of aim is at and to work on that consistency.
Here's a clip from Dynasty Dysected where Todd Martinez explains the marker position with barrel in line with your nose.
Todd explaining how to snap shoot.
Another thing to do if you don't already do it is to use your extra/left over paint to practice your snap. If you have some paint in your hopper as you start heading back to your staging/air fill area use it to practice snapping at a small post or cone. At my local field we have pairs of 1.5" posts that mark the starting gates on each airball and rec-field. On the airball field before I head back in I'll pick whichever type of bunker on the back line I need practice with and snap from it to shoot back at one of the posts. On the rec-fields I'll try snapping at one of the posts or the tip of a 4x4 that's part of the fields bunkers. As a side note, I find that this also helps when learning how to shoot on the move. Pick a tip of a post or a small target, I like posts because there's really no room for error, and try hitting it as you walk by. As you get better start building up your speed as you move past the target.