Instructions
Select "Multiplayer" from the main menu and then choose "Online" or "Live."
Choose the "Create a Class" option and select "Claymore" as your equipment.
Select the "Killstreaks" option and select "Care Package" and/or "Sentry Gun." When you get the necessary killstreaks in the game (5 and 6, respectively) these will be airdropped to you in crates.
Start the match and play as you normally would. As soon as you get a crate, walk up to it and place your claymores around it. When enemy players try to steal it, they will be killed by your booby trap.