What’s your Call of Duty: Black Ops advice or tip?

If you are having a hard time in multiplayer, try the Famas. Its an assault riffle available early on that packs a real punch

Playing Domination? Got some C4? Throw some on the flag you just captured, wait around the corner or in a nearby building and wait for the other team to try to capture it, then let it fly! (Hint: If you can, try not to throw it directly on the flag as experienced players will look for the C4 "light" and shoot it. If there is a nearby obstacle or vehicle close enough to throw it under that is close enough to still kill them, throw it under there instead.)

If you want some extra speed when running, switch to your pistol temporarily until you get to the area you want to get to, then switch back to your assault rifle, sub machine, etc.

In the Gun Game wager match type, it's very important to get your first couple kills as early in the game as possible. Otherwise, you'll be firing your pistol against a dude with an AK47... :)