I just bought the Call of Duty Black Ops, and I was excited to play the multiplayer part.
Unfortunately my experience was that the multiplayer part did not run very smooth. I searched the internet a lot, and I was amazed to find a solution that helped me.
1) Start the game
2) Find the console (½) next to "1)
3) Type cl_maxpackets 100 (default should be 30)
4) Close the game
5) Once you reload the game, double check that it is now 100
Bang, it now runs smooth :)