[Domm2501]

Hm...basicly everything is said allready :| Damn...
Oh well,maybe one point not :P
Try to adapt yourself to the weapon you use...don't play with a rifle like you play with a SMG...
And mindgames are also very important in this game,I think.
Try not to always just rush into your enemy,try to make yourself an advantage,like coming from behind,shooting at people that are in a gunfight from further away,something like that.
And never camp...camping is totally USELESS in this game...
As for the grenades, drop/throw them at the direction,where the enemy is moving.
I might aswell add some karabiner infos :P
Playing against a karabiner:
Dodge(=croach) a lot! Karabiner ALWAYS aim for OHKO spots close up/mid range,and those are head and upper chest. So if you croach,they'll shoot right above you. This requires some timing though...because if you croach all the time,then the karabiner will adapt :P
So,you have to croach,stand up,croach,etc.
The further you are away,the less inaccurate the karabiner will be.
THough it still can be pretty lethal from a great distance (most longrange kills you'll get with karabiner are OHKOs).
Erm...yes,about the mindgames...it's just simply thinking like your enemy :P
Like:"I'm rushing at him now,going to reload now...dragging out a nade." etc,etc
And try to find your own style...don't just copy others,because they are uber agressive and get loads of kills,many people preffer playing defensive aswell :P
(Such as myself)
But you can also win games if you play defensive :P
You don't have to kill many people,if you die less ^^

Edit: Last point to add would be play,play,play...not every person is a nature at gaming :P