I will add a little to this as mid-long aking is by far what Im best at.

- First off dont crouch. In long to mid range anyway. The ak is more than acuret enough for 1-2 bullets standing up. If you crouch any good player will take you out.

- As said above the key is sidestep pause shoot sidestep pause shoot. This is when you are in the open. Bare in mind this pause doesnt have to be long. With practice it will get quick and quick. Try not to aim on the pause. Aim as you move. Kind of step into line with the target. This will make the pause smaller and lower the chance of getting shot back.

- Timing, Consider two akers at distance. Sometime you will find stiuations in which 2 aks are side stepping and shooting but both are just out of time with each other and niether hits. In this case try to sitch your timing to his on the sidestep you take the shot. Bit of a hard one to explain but I think you will no what I mean if you have been in the sityation.

- shooting a dangerous oponent from cover. This is tipically an awper. You could just be low on health or pinned in by a good aker. In this case you cant show you self for long or you die. The trick here is to sidestep out and shot where he was the last time you saw him. Basically you are shooting blind. Dont try to reajust your aim. Just shoot 1 bullet and step back. During that side step you will see his new position. On your new step shot there and so on. This can be done fast that anyone can react.

If you are the awp remeber to move a little everytime you are seen. It doesnt have to be much more than a foot. Just enough to stop you getting your head take off.

-Close range. with in a few meters you can get away with spraying with the ak. As the distance increase you will need to drop your aim to his feet to maintain the shot.
Another option is to use your first spray straight at him (while moving to the side idealy at this range). If you miss or another CT comes drop to a crouch which will bring some of your accuracy back and spray straight at them (not the head). This works well however if you miss this last time your dead.

M4 is simlar except its better at close range (especially with silencer) and worse at long range. Both are more than suitable for all situations however.