THESE ARE THE ITEMS IN THE GAME AND WHAT THEY DO

banana	-Cause you to spin out. You can drop the item by pressing the button or throw the banana in front of you by pressing up on the controller and then pressing the button. There are two ways to spin on a banana. The first is the imediate spin when you hit the banana while slightly turned. However if you hit the banana while going straight you have a second where the kart wobbles back and forth before you spin out. To stop yourself from spinning you must press the break during the wobbling animations. If done sucsesfully you will see a small musical note appear above your characters head and you won't spin out.
banana bunch	-Similar to the single banana however the bunch trails behind you after pressing the button once and you can either drop them one at time throw them one at a time or swerve into people and then lose all the bananas when you hit them.
green shell	-Shoots out in a straight line. Can also be shot backwards if you hold down the controller and press the button. Not very effective at long distances.
3 greens	-This item causes three green shells to circle you and protect you from any objects that may be on the track. They can be shot away one at a time but unlike the single green shell these can only be shot forward.
red shell	-A red shell is much like a heat seeking missle. It is very fast and it will quickly home in on the nearest player in front of you. Just make sure there are not any walls or other obstructions in the way of it that will cause it to stop.
3 red shells	-Causes three red shells to circle you protecting you and each shell can be shot off one at a time.
mushroom	-Gives you a temporary speed boost. These are most effective when you want to cut accross a section of the course that would normally slow you down. If they are just used on the track they are not nearly as effective.
3 mushrooms	-These are the same as the single mushroom however you can use three at any time you want. These are effective for larger offroad shortcuts.
unlimited mushroom	-With this you will have an unlimited amount of mushrooms for aproximatly 10 seconds. Remember that once activated you only have 10 seconds until you lose the item.
fake box	-This is used to trick the other players into thinking it is a regular item box. When a player hits one they will fly into the air losing valuable time. Plant these next to real item boxes to confuse the other players. Remember, the only difference is that the question mark on the box is upside down.
boo	-This will steal the item from the nearest player to you. After using it you will be invisible for a short time and you can safely pass through bananas and shells. If you are in first place these are the best item to get since the computer always gives the players behind you better items in order to catch up to you. As soon as they get something you need use the boo and increase your lead.
star	-You will be invulnerable to bananas and shells for a short time. during this time you will have better speed, handling and you can crash into the other players causing them to spin out
lightning	-This will cause the other karts to shrink. When small they are much slower and if they collide with any other player or object (tree, stone, plant) they will get crushed.
spikey blue shell	-One of the most interesting items in the game. When fired it will seek out the player in first place and along the way if it hits anyone it will wipe them out and keep going. the only thing that can stop a blue shell from hitting you if you are in first place is to drag another blue shell behind you and if you are in first place it is very rare to get a blue shell.

For info on the best places to use the items check out the CUPS section.