Im just going to say that you have to play smart 
Tips (I know what I say sounds obvious but when i do it, people start QQing):
1)In GM, when an ally dies, shot around his dead body, or throw a grenade.
2)If you get flashed, dont spray and hope to hit something. Look at the minimap and run behind the closest wall/cover.
3)If you're bad at bursting, and if the enemy saw u, run behind a wall, wait till the enemy gets near, and spray like crazy!
4)Camping, dont care if they call me a noob, i get kills.
5)Try to go around and backstab the enemy
6)In GM, pretend to defuse the bomb, run back and shoot all ghosts who came at u
7)Throw a grenade under yourself if you're defusing (wouldn't recommend it)
8)In S&D, if your GR, and you get to the bomb site, camp around the bomb and kill all BL, since they will be trying to get in in all possible ways and they will probably run out in the open.
9)If you know an enemy is behind a box, dont wait for them to move, spray at the box.
All i can think of for now..

Tips (I know what I say sounds obvious but when i do it, people start QQing):
1)In GM, when an ally dies, shot around his dead body, or throw a grenade.
2)If you get flashed, dont spray and hope to hit something. Look at the minimap and run behind the closest wall/cover.
3)If you're bad at bursting, and if the enemy saw u, run behind a wall, wait till the enemy gets near, and spray like crazy!
4)Camping, dont care if they call me a noob, i get kills.
5)Try to go around and backstab the enemy
6)In GM, pretend to defuse the bomb, run back and shoot all ghosts who came at u
7)Throw a grenade under yourself if you're defusing (wouldn't recommend it)
8)In S&D, if your GR, and you get to the bomb site, camp around the bomb and kill all BL, since they will be trying to get in in all possible ways and they will probably run out in the open.
9)If you know an enemy is behind a box, dont wait for them to move, spray at the box.
All i can think of for now..
I can get headshots anytime. 
