Don't spray and prey. Even though everyone does that, accuracy is crucial as 2 to the head is cheaper then 5 shots in the chest or leg
Don't be stupid and combine contradicting perks with weapons (I.E. Use ghost but have no silencer, have scavenger but you camp like a bio-tch, ect)
ANY optical sights is much better then iron. Also, "improved sights" for pistols is a waste, don't ever use it.
Buy killstreaks you know you can reach. Don't be stupid and buy the last 3 killstreaks or buy all the killstreaks. Buy the ones you know you will get.
When playing hardcore, keep in mind that even if the entire other team are howler monkeys, they ARE and WILL be using turtlebeaches and/or modded controllers. So for Christ sake, use ninja and ghost with a silenced weapon (In hardcore, it's one scratch one kill so sights arnt of high need but accuracy is still needed to prevent excess shots to reveal your position)
On hardcore, use a 3,4,5 killstreaks setup cause there is no way in hell you can get 8 or 13 kills without dying. Also keep in mind that if the other players are smart, they will pick this setup aswell
Claymores: Aim it toward where the person is heading or at the halfway point. HIGHLY recommended for choke points like doors and windows but innaffective in open areas (you might get lucky but it's a waste)
These are most the tips and tricks I learned as a COD veteran and you can implement this on any COD game.
