So far good and valid points I've seen here. The biggest things that are going to contribute to good shooting habits have pretty much been covered here. Biggest things to remember and train on that have been said are stright foward. When engaging your target or Targets, first and foremost is going to be cover, find the best available and get to it, from here you can use more "precision" even though it is a hard thing to get from a standard marker. Square off against your target, giving them the smallest target possible by slightly shifting the NON-Shooting side of your body towards your target. Your stance is a fairly big contributing factor to this as well, even though you are shooting a marker that has virtually no recoil, it is still best to position your firing side leg towards the rear of your body, slightly bending at the knee, as well as postioning the non-fring side leg towards the front in the same manner. TUCK YOUR ARMS IN!!!!! Biggest thing, as I have seen many of players tagged out (Inculding myself) when behind a covered position becasue their elbow was out providing more of a target.
And as for the trigger pulling, well, though it does not have a HUGE impact, lern to pull the trigger properly, do not GRASP the trigger using your entire finger, only the tip should be firmly against the trigger and pulling, and if you got a "Gorrilla Powered Hand" this is kind of important, as using the entire finger shifts the gun in the direction of pull, thus bringing your aim more off target. Shoulder weld (If you use a stock) should be practiced routinley, mainly practice shooting targets from a ready to fire position, this involves having your gun generally pointed near the ground with the stock somewhat fixed to your shoulder as most of you probably do when moving. Practice shifting from this ready position to the fire position, this way, you know that when you snap your marker into postion to fire, you are not just guessing where the rounds "may" go.

And the thing I guess to remember also is that, no matter how good your training in this is, it is after all, a paintball gun, and we all know what the going rate as far as accuracy is to begin with, and sometimes, it doesnt matter what you do, or how good your tactics and "habits, sometimes its just luck of the draw.