For the love of God DON'T DIE! It's fine if your not the best not everyone can be, but just try and die less. I'm fine if you only get one kill in around of survival, I'll get the other 9. If you see more than one person looking at you, run, if you get shot first in a one vs one firefight, run, just stay alive. Never poke out of leave cover when your not at full health, always wait for the health regeneration. There is nothing worse than me starting a match with a quick 5 kill streak then dying once and being kicked out of the round. On respawn don't just go running into the fray, take a moment to see if a teammate is just about to spawn, wait for them and go together. In countdown if, for example, it's a 2 on 1 and you have to defuse a lit charge, and you know your teammate is better than you, right away go for the defuse, when the ennemy pops up to kill you defusing I'll kill him and worse case, you die but I'll still have time to defuse. A sacrifice to win the round. And each round look to see who is the top person on your team, when the next round starts, follow them everywhere. Bad players just tend to wander around the map aimlessly, good players are always going somewhere specific. And guard that heavy ammo, when it doubt, play that heavy ammo area, do not let them get it, it is incredibly important.