If you want to up rank faster then KC is the game to play, pick up both yellow and red tags. Now, if you don't care about your kill/death ratio (or have fun) and just want to rank up quicker there is a way to score 5,000-6,000 points per game, by collecting your own tags you get +250. So the goal is to keep collecting your own tags in order to gain massive amounts of score and EXP.
Try to find a spot where the enemy can find you easily,put down a tactical insertion,stand on your insertion, soon as you die quickly skip the kill cam and collect your tag.
you will prestige from 61-80 in no time but your kd ratio will be very low. I have played a few games with some guys doing that and he ended up with 2-30 but he got about 8,000 points that game.
Required:
Tactical Insertion (Level 61)
Quickdraw Pro