Hey I just read your shout about assaulting tips.
Here they are:
Make a habit of keeping your aim at neck level.
Never shoot more than 3 bullets at once if holding an M4a1 and never more than 1 bullet when holding an AK47. If you become good at this type of bursting, you will be able to shoot fully armored + full health enemies with single bullet shots easily.
If you are playing at a very high sensitivity, lower it down, even if you have a habit of high sensitivity. If you lower it down and your hand is settled at that lower sensitivity in a week or two, then your aim would become very stable.
Always try to strafe left and right to shoot enemies instead of moving aim left and right. Cuz moving aim left/right could move it up/down too resulting in loss of headshot accuracy. I never move my aim when fighting one on one with an enemy. Rather I actually move to the left/right to align my aim with his neck.