What is the fastest way to rank up on Call of Duty Modern Warfare 2?  

TDM Express.. Drop at least 15 kills a game, anywhere from 3000-6000 xp in usually around 6-7 minutes, depending on what kind of bonus you get of course. Then you do it all over again in less then 15 seconds.

More suggestions: http://gamebattles.com/forums/t/2611132.html

Hope that helps.

depends, wanna chea tot do it or wannna be real?? if u wanna cheat id say co to gage match (as long as ur lvl 19) and get a mic. say head shots??? and if you and they agree you take turns shootin eachother in the head. you actually get loads!! of points and titles and embelems and stuff. be real??? just play search and destroy, but u godda b good at it. for newbs id suggest the at4hs and noob tube, plus c4 (or grenade) then run around and ur practically a ticking time bomb!!! p.s if u have ps3 add me- Gseaton

The best wy is to get someone to boost with you. You cage match with a riot shield and an Amy and just take turns shooting eachother. You get tons of xp and it's insanely fast!

I saw a video on youtube re: experience boosting with riot shield.
But your team and your opponent's team must have a pre-agreement prior to the match that all you have to do is boost experience and not kill each other mercilessly.
Go check it out.

Cage match was a good place to earn massive experience too.. unfortunetaly, Infinity Ward remove this with their latest update.

Headquarters Pro or Domination according to your preference. I prefer Free For All's though but make sure to always use different kill streaks and to use other guns once you've completed the challenges for one of them. This way you will always get more exp.