Movement:
Your movement should be super-fast. There are two scenarios in which you need a super-fast movement.
The first scenario is that you are running in an open area, and you know you can't run in a straight line so, what you do is run while moving left and right.
The second scenario is that you are in a fight with the enemy. The chances are you will die if you are not moving while firing. During a fight, don't just stand in one place; always move and fire at your enemy. It increases your chances of killing your enemy or get less damage.
While you are moving during a fight, your enemy won't be able to focus fire on you. Your enemy will either stop firing or run out of ammo before even dealing with single damage.