How to level up the fastest in black ops?

They have Nerfed demolition. Which means, They have lowered the exp. You only get about 5,000-7,000 exp in one game. However, They have not Nerfed Capture the flag. It takes a while to get used to, but if you have good games you could get around 15,000 exp. Or 25,000-40,000 exp with lots of decent challenges. Try the AK74u, Its overpowered. 3 - 5 hit kill. Takes 1.2 seconds to kill someone, on average.