Well, when you get to a turn, press B (It works on the GameCube Controller, Wii Remote, and Classic Controller). But, when you have the Nunchuk, press Z.
By Beating cups
When you hack the game.
Get gold trophy in grand prixs to unlock karts and characters.
They Are Exactly the same cups in the same order as Mario Karts DS
You do an amount of races or you can finish cc's.
by getting good times on each track.
That's completely opinion based.
Pressing the + button.
King Boo, Bowser, Dry Bowser, Rosalina, and Funky Kong all use large karts on Mario Kart Wii.
Karts. It can have longer turbo boosts.
No there is not another mode after mirror mode
you have to complete certain things to unlock stuff. this website shows you how to unlock everything, including karts. http://www.videogamesblogger.com/2008/04/18/how-to-unlock-all-mario-kart-wii-secret-characters-bikes-karts-and-more-guide.htm