How to quickly rank up in Modern Warfare 2

Quickly, ranking up in Modern Warfare 2 is really easy. The secret is to focus on completing the challenges since they give you a lot of experience points. As you unlock an achievement you should try to unlock another one and so on. Additionally you should try different gametypes as some give you more experience points than others. Usually, I get more exp. in Hedquarters Pro than in Team Deathmatch.

If you are really eager to rank up you can boost by assembling a party of 8 to do Free For All and take turns getting points.