Instructions
Play game modes like "Team Deathmatch," "Domination" and "Search and Destroy." Each kill in "Team Deathmatch" will give you 100 experience points. Capturing a point in "Domination" will give you 150 points, defending a position by killing an enemy trying to capture your point or killing an enemy while capturing their point will give you 200 points and killing any enemy will give you 50 points. Killing someone in "Search and Destroy" will give you 500 points and arming or disarming the bomb will give you 1,000 points, however "Search and Destroy" can be difficult to master, as you only have one life per round.
Purchase and complete contracts. The contracts can be purchased in the game menu under the "Create a Class" option. The contracts change each week and are essentially special challenges that when completed will give you a extra experience and often times extra COD points that you can use to purchase weapons and attachments. The more difficult the contract, the more experience and COD points you will receive. You can purchase three contracts at the same time.
Complete challenges to earn extra experience points. Go to the "Playercard" menu and select "Challenges" to see what challenges you have yet to accomplish. Each weapon, game mode, weapon attachment and killstreak have their own collection of challenges, like getting five headshots with an SMG or shooting down a certain number of enemy aircraft using the Strella rocket launcher.
Use all of these ways to earn experience points together. Purchase contracts that apply to game modes that will give you the most experience and weapons that you are skilled with or that you're close to completing a particular challenge with. For instance, you can purchase a contract for winning a certain number of "Team Deathmatch" games, another contract for getting kills with an SMG if you only need a few more kills to accomplish an SMG challenge and a third contract for calling in killstreaks or another easily accomplished task. You can now rack up an insane amount of experience points playing in only one or two games.