This should help all players, not just snipers. There seems to be a lack of knowledge of popper shooting techniques. This is the military way.
Mods, please sticky this.
In the army they teach BRM, basic rifle marksmanship.
The 4 fundamentals of BRM are, steady position, sight picture, breathing, trigger squeeze.
First you need a stable firing position, as for snipers, laying down, weapon on a bipod, or sandbag, or something that will keep it steady and in the same position. You need to keep your head on the same portion of the rifle EVERY TIME you fire. This will also help sight picture.
Sight picture, is what you see through the scope, or down the rifle, or what ever you use. This needs to be consistent every time. Other wise your shot groups will be all over the place. Place the reticule on the target in the same spot; keep your cheek and hands in the same places on the rifle, every time you fire.
Once you get those 2 down, the rest is easy. Breathing and trigger squeeze is the same step, as you pull the trigger. Breathing first, you will time the shot to your breath, not your heart beating. They taught us to fire on the out breath. Inhale evenly and exhale, when you exhale, empty your lungs; stay just like that until the shot is out. Then continue to breathe normally. When taking multiple shots, you can fire on both ends of your breathing.
The trigger squeeze should be even and not jerky. Even the slightest jerk, will throw off the rifle, which will send your round some place other then intended. As you hold your breath squeeze the trigger, using the tip of your index finger. Using the tip helps, because it is the most isolate joint, and will not move the rifle if done properly. Increase pressure as the trigger comes back. DO NOT anticipate the shot, wait for it. If you anticipate, you will flinch, and or tense your body up. Which will move the rifle; its a slow gradual squeeze that should feel natural.
After you fire the shot, do 2 more. So you have 3 holes in your target. You want them to be with in a certain distance of each other. US soldiers are expected to put 3 rounds inside a quarter (25 cents) at 50 meters. Snipers are expected to hit a target 700 meters away 90% of the time. Normal soldiers usually hit 300 meters 10% of the time. Big difference
Once you have your groupings here is how you adjust. If you achieve your set distance groupings, say 3 holes with in a quarter, but it is not in the center of the target, adjust your sights. It means that the shots were consistent, but the sigh picture is off. Adjust to the direction that will put the rounds closer to the target and fire again, and then adjust, until you are dead on.
If you have rounds all over the place, make sure you have a steady position, and take careful care to have the same sigh picture.
If your rounds are all on the same horizontal level, but one is higher then the others, that means your breathing was off.
if its the flip side of that, and one shot is to the left of right of the grouping, your trigger squeeze was off.
I hope this helps, and gives you all something to train up on.