Black Ops: Help me for getting more xp?

Yes you are earning a good amount of xp per game. Search and Destroy offers the most xp per game. Each kill gives you around a thousand points i believe. Demolition is, well, demolition. It consists of mannnnnnny explosions. To succeed in this game mode i suggest making a demolitions class. I usually use an assualt rifle like the commando with a m203 grenade launcher. Also set perks such as flak jacket to protect you from explosions. For secondary i always use a launcher for demolition. Oh and c4 works nicely as well. Have fun!