really fun game, it is very violent just warning u but it is awesome, there is a zombie mode and it has a very good storyline, way better than reach or brotherhood
-stick with the AI, but don't mirror them. Like WaW, they tend to pick the better cover, and if you're there first, you get trapped...
-Common sense. I cannot stress this enough. Recruit may just be run-n-gun, but hardened and veteran can really nip you in the bud if you play stupid. And online, its how I got my 1.27 K/D Ration in MW2. Its not great, but I'm consistent. I play smart, I kill smart, and I support my team, so they support me back(by winning)
-Slice the pie: Going into a room or around a corner, crouch, and just slowly poke your nose around. Go real slow, and maby a flash bang for good measure.
-Watch your minimap. It shows were your enemies are. And if you cant see them (UAV Jammer or whatever its called), and they kill a friendly, a big green dot is gonna be gone. I always stop, and watch the most obvious point of entry. This helps as I don't get T-bagg'd in prone, or embarssing knife kills.
-COMMON SENSE! I know I said it before, but if a place looks too open, too safe, too quiet, its a trap. I dont care what ANYBODY says, I just go around. And even funnier, is when you give THEM the embarrising knife kill.
-Don't get sucked down your scope; watch your map, and dont watch the same place consistently. All good camping spots have multiple avenues of approach, and I use my claymores as a warning, and possibly a kill, so when I hear them go off... heads up.
Multiplayer tip, first you want to learn the maps, theres a game mode called combat training that u face computer bots online. This will help you learn the basics of the game, what its like, and you can change the dfficulty to whatever you like so if their too hard or too easy.