Official Twister Rules

So here goes, straight from the the good people at Milton Bradley.

Setting up the Game

Spread the mat faceup on a flat surface, indoors or outdoors.
Players take off their shoes and set them aside. If you're playing outdoors, you may want to anchor the mat corners with your shoes.
Designate an extra person as the referee. The referee is not considered a player; during the game, the referee will spin the spinner, call out the moves, and monitor the game play.
Position yourselves on the mat according to the number of players, as explained below.

For a 2-player game: Players face each other from opposite ends of the mat, near the word Twister. Place one foot on the yellow circle and the other foot on the blue circle closest to your end of the mat. Your opponent does the same on his or her end.

For a 3-player game: Two players face each other on opposite ends of the mat, near the word Twister. Each player places one foot on the yellow circle and the other foot on the blue circle closest to his or her end of the mat. The third player faces the center from the red-circle side of the mat, placing one foot each on the two middle red circles.

How to Play

The referee spins the spinner, then calls out the body part and the color that the arrow points to. For example, the referee may call out: "Right hand, red." All players, at the same time, must then try to follow the referee's directions as explained below.

Each player must try to place the called-out body part on a vacant circle of the called-out color. For [example, if the referee calls out "Right hand, red," each player must try to place a right hand on any vacant red circle.
If your called-out hand or foot is already on a circle of the called-out color, you must try to move it to another circle of the same color.
There can never be more than one hand or foot on any one circle. If two or more players reach for the same circle, the referee must decide which player got there first. The other player(s) must find another vacant circle of the same color.
Never remove your hand or foot from a circle unless you're directed to by the referee after a spin. Exception: You may lift a hand or foot to allow another hand or foot to pass by, as long as you announce it to the referee beforehand, and replace it on its circle immediately afterward.
If all 6 circles of a color are already covered, the referee must spin again until a different color can be called out.

Strategy: Try moving toward an opponent's portion of the mat, forcing the player to go over or under you to place a hand or foot!

Being Eliminated

Any player who falls, or touches the mat with an elbow or knee, is immediately out of the game. (If you feel that a new position is impossible, or will cause you to fall, you may elminiate yourself.)

In a 2-player game, the game ends and the remaining player wins. In a 3-player game, the remaining two players keep playing until one player is eliminated and the remaining player wins.

How to Win

The last player left in the game is the winner!

Team Play

For a 4-player game, form 2 teams of 2 players each. Teams face each other on opposite ends of the mat, standing side-by-side with each foot on a circle so that all 4 circles closest to the Twister name are covered.

Just as in a 2- or 3-player game, the referee spins the spinner and calls out a hand or foot and a color circle. Play as in the 2- or 3-player game, with this exception: members of the same team can cover the same circle with one hand or foot each.

As soon as a player falls or touches the mat with an elbow or knee, the player's team is eliminated and the other team is the winner.

2-Player Game with No Referee

If there are only 2 players and no referee, you can play without using the spinner. One player calls out the body part; the other player calls out the circle color. Players alternate turns calling out the body part first. Otherwise, game play is the same, with the last remaining player the winner.

Party Games

Round Robin: Form several 2-player teams. Each team, in turn, plays every other team. Players keep track of wins and losses. The team with the most wins wins!

Elimination Game: Form several 2-player teams. Play against each other, with losing teams dropping out. Winning teams play each other until only one winning team is left!