Radar. Radar is your best friend. Also, a quick trigger finger is important. In cqb, a split second is what can make or break you. Be aggressive, and use cover to your advantage. Scenario: someone is shooting you from the B flag on Firebase while you're at A side door facing B. You can either A: rush the guy, often resulting in a death or B: go around, and jump down to B using that window close to the ceiling. B is the obvious choice, because it greatly increases your chances of surviving. Shape the map to the way you want it, and you'll have killstreaks as long as you can possibly imagine. Felwinters Lie is my absolute favorite shotgun, it's the sniper of shotguns. Also, another thing, always be ready to use your melee. Shotguns were built to kill in one single blow, and missing that shot can kill you. That melee is a last resort optiom that has saved me a million times.