Instructions
Locate cheat codes on the Internet for the game you are playing. You can use the sites in the Resources section for starters. Most sites have cheats organized by game.
Jot the codes down or leave the webpage open.
Insert the game disc into the Wii and begin your game.
Follow the instructions for the Wii cheat code to obtain the desired effect.
Input the button combination if the code is a sequence of buttons. If the webpage indicates that you need to pause the game, open the Plus (+) menu beforehand. You need to press the buttons rapidly, not leaving any space between the button presses.
Find the cheat menu or code-entering system. In some games, the cheat menu is hidden in the pause menu; in others, it's in the game's hub world. These will often request a code or pass phrase that unlocks hidden in-game content. For example, LEGO Star Wars has a codes command hidden in the Cantina -- locate that and input "ACK646" to unlock Admiral Ackbar.
Meet the criteria for the easter egg or other unlockable content, and the game will automatically reward you. For example, when you reach Pro level in Bowling on Wii Sports, the game gives your character a diamond-encrusted bowling ball.