A really good fast way to boost in MW3 is to go to a 1v1 Faceoff lobby alone, then invite your friend. Keep trying until you find Kill Confirmed. You and your friend vote on that. Once you get in the game, one person gets 14 kills, and let their friend have the tags. But, you need to get about 4-8 of them so you will not get banned. Then, once you get 14 kills, let your friend get 14 kills, and let him get about 4 to 8 of your tags. Just an idea!
But my opinion, spawn trapping can be a really fast way to get banned, just heads up.