Due to the realism designed into the game, aiming and firing weapons is not simply a matter of point and shoot, unless an enemy decides to sit right in front of you.
Unsighted fire is subject to an ‘Accuracy cone’ that spreads based on the weapon used, stamina, suppression, and other factors. That is to say, if you have not been sprinting and are using an M4, your spread will be very tightly controlled. If you have been sprinting extensively with an M249, your spread will be very large.
Sighted fire is governed by sway and recoil control, with minor accuracy cone spread on certain weapons. That means that the round will go roughly where the sight picture indicates. Sprinting will increase both your sway and recoil when aiming and firing, as will the amount of suppressive fire you are under. In either case, it is generally best to fire in controlled bursts.
One more influence on proper aiming is bullet drop. This is only apparent in long-range engagements and affects rounds of different calibers accordingly. That means the 5.56x45mm round fired by the M4 and M249 drops more than the 7.62x51mm round fired by the M14EBR-RI – the larger 7.62x51mm round is accurate much further out, meaning it drops much more slowly.
If you run out of ammo, you can always find a buddy and take spare ammo with [E] key by default. This spare ammo is not taken from your buddy’s inventory, so it’s a win/win.
Aiming with a controller is more difficult than with a mouse simply due to the mechanics of the two systems. To help combat the game pad's inherent difficultly aim assist is implemented. Aim assist consists of two systems, sensitivity and magnetism, which complement one another.
Sensitivity is a measure of how quickly the crosshair moves in relation to the amount of input on the analog stick. In a scenario with no targets sensitivity is constant - moving the stick a little moves the crosshair a corresponding small amount and similarly for a large movement on the stick.
When a target is in view however, as the target is closer and closer to the crosshair the lower sensitivity gets. The effect is slower crosshair movement across a target
Magnetism is the tendency of the crosshair to "float" towards a target near the crosshair. The closer to the crosshair the stronger the attraction.