The first thing you do before you shoot is seek a stable firing platform. You can't shoot properly if you're unstable. The two main things that affect stability are firing posture and gun support.
In the prone position, you present a very small silhouette to other players. It'll be harder to spot you if you're in the brush. It gives you the most stable firing posture with or without a gun support (sandbag, stump, etc.). On the downside, it's got the lowest available mobility. It's harder to move out of your position in the prone.
While sitting, you give yourself a stable firing platform by resting your elbows on your thighs and present a small target to other players. It has low mobility but is slightly better than in the prone. Most comfortable posture.
Offers you a not so stable platform but gives you good mobility and a relatively small target. From this position, you can move to another position quicker than in the sitting or prone position. Knee pads would make it more comfortable for play on rough terrain.
Second least stable but second most mobile while presenting a medium sized target. Fatigues the legs faster if you're not in shape.
Offers the least stable posture with the largest size target to your opponents but is definitely the most mobile. Use it with good cover (large trees, tall bunkers, etc).
Use a support to steady your aim if you have it. Be it a branch, a stump, a sandbag, or anything that you can rest your gun on to steady it. If none is available, your arm, chest, and shoulder muscles will have to do the work in steadying the gun. The good thing with a branch is it doesn't tire out as fast as your muscles.
There are some rules to keep in mind when using supports. The first is to never let anything touch your barrel. Never support your barrel on a tree branch or rest it on a hole in a bunker. The force applied to the barrel by resting it on something may be enough to misalign it.
The second rule is the hard-soft rule: always support something hard with something soft. Example: your weapon is made of hard material so support it with something soft -- a sandbag or your hand. What about a tree branch? Well that violates the rule (a branch isn't exactly soft), so instead, use your hand as a buffer between the branch and your gun. Using a soft support for your gun allows the gun to conform and rest snugly against its support.
When you look through your sights, you should have what's known as a "proper sight picture". Whether you're using basic iron sites or more advanced dot sights or scopes, what you see through them will determine a hit or miss. The following illustrations will show the proper the sight pictures of various sights.
Align the edges of the front and rear sight posts. Some sights may have aids to help you do this -- like the white dots as seen in the illustration on the right. Aim center mass of your target at normal ranges. For shorter ranges, aim lower while for further ranges, aim higher.
These are really easy to use. Place the dot on the target, center mass just like with iron sights. You don't have to worry about parallax like with normal scopes. As with iron sights, adjust your aiming point for the appropriate range.
Scopes are a little bit harder to use. You have to make sure you get a good sight picture to prevent parallax. Again, aim center mass and adjust for range.
Even with good stability, your gun will still move around ever so slightly because of your breathing. You'll notice this as you try to obtain a good sight picture -- your sights will seem to float up and down as you breathe. You'll notice it more in the unsupported standing or crouching positions than in the prone. To overcome this, breath control is essential. The only way to control the up and down floating is to simply stop breathing. Numerous options are available and you really should adopt the technique that you're most comfortable with. When you hold your breath, you should be able to shoot within your comfort limit. If you begin to starve for air, you're not doing your shooting or yourself any good, so start the whole process again.
Full LungsTake a few deep breaths to calm and focus yourself. When ready, inhale, hold your breath, then shoot.
Empty LungsTake a few deep breaths to calm and focus yourself. When ready, exhale, hold, then shoot.
Half Full LungsTake a few deep breaths to calm and focus yourself. When ready, either exhale or inhale to about half your lung capacity, hold your breath, then shoot.
The actual act of shooting is done by pulling the trigger. Actually, the correct term is squeezing the trigger. It should be a nice, smooth, controlled action. Don't jerk the trigger. The shot should almost come as a surprise. Improper trigger pulls will lead to shots pulling to your shooting side -- if you shoot with your right hand and jerk the trigger, the shot will pull to the right. When squeezing the trigger, use only the fleshy part of your fingertip. Never wrap it around the trigger as this also pulls and misaligns the gun as you shoot, leading to missed shots.
A good way to practice good trigger control is the coin test. To do this, you should be able to dry-fire your gun (not really possible with an AEG). Take up a good shooting posture and support your gun -- prepare as if you were really going to fire. Have a friend place a coin on the barrel. Use whatever breathing technique you prefer and squeeze the trigger. Done properly, the coin will stay on the barrel, even if the guns internals (hammer, bolt, etc.) move.
Ok. You've done everything right so far: posture, support, sight picture, breathing, and trigger pull. You're not done yet. A few moments after your shot, it's important to keep the same sight picture. Follow through with your shot. After pulling the trigger, the bullet still has to travel down the barrel. Any change you make in the very short time between pulling the trigger and the bullet leaving the barrel will ruin your shot. Following through with the shot ensures that the barrel is still aligned with the target after you pull the trigger.