Instructions
Put your "Black Ops" game disc into your system and allow the game to load to its main menu.
Select "Multiplayer."
Select "Xbox Live" or "PlayStation Network" (depending on the console you are playing on).
Highlight your name from the list of players in the lobby on the right-side of the screen. Select it with the "X" button (on a PS3) or the "A" button (on an Xbox 360). Your current player card will appear.
Highlight your current clan tag and select it to bring up the editing screen. Use your controller to change your clan tag to display the current name or symbol for your clan. Select the "Previous" option on screen to complete changing your clan tag.