Yeah I'd say strafing is a must especially if your talking older games, newer ones not as much since theres a lot of waiting behind walls or peeking around corners so its usually slower especially online all those damn campers :p but just something if it's possible use as high a sensitivity you can handle and still be fairly accurate and get used to the tactical controls in COD and any other game that offers it. The benefit of hitting the ground quickly outweighs the deaths you get from slower melee. Those are the only general tips I got besides the aim at him and fire and let experience make you better.