n every FPS game are things named Recoil and Bullet Spread. In Counter-Strike each gun has a different program for Recoil and Spread. Some guns have max recoil but little spread, some have max spread AND recoil and so on.
The main gun for Terrorists is the AK47 and the Counter Terrorist equivalent is the Colt or M4A1. These have great power with lower recoil and spread.
To reduce recoil and spread crouching is the best option. Crouching while shooting will make sure that your bullets will be closer together. Tap-shooting is another option. To tap-shoot you use your mouse to burst out 3 or 4 bullets with a slight stop then shooting again. It minimizes the recoil if you combine these two things.
Tap-shooting works on the run but it still wont be as effective as crouching. Whenever you are staying still to shoot always crouch.
You can check out how much recoil and spread you are going to get by looking at your crosshair. The bigger it is the less accurate.