This is a link to the rules of American croquet (also called six wicket).  http://www.croquetamerica.com/croquet/rules/american/ 

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The following link contains the complete Rules of Golf Croquet.

http://www.wcfcroquet.org/Files/WCFRulesofGolfCroquet(2005Edition).pdf

 The balance of this report will highlight common rules which come up regularly   Hopefully this will  minimize some confusion for new players.

Order of wickets

The route through the wickets is the first area.  We usually play a 12/13 wicket game.  We normally play twelve wickets, and then play a thirteenth wicket if a tie exists after twelve.

The route through the first six wickets is shown in the diagram above.   The route through the second 6 wickets is shown below.  If a tie exists after twelve wickets, the thirteenth wicket is played in the order and direction shown.

Jump shot

Defined as striking your ball in such a way as to cause it to jump over another ball.  This shot is not addressed in the rule set above, but it is considered a legitimate shot in other croquet games.  For this reason it was decided that it will be permitted.  ( Note: The rules inflict penalties for shots which cause damage to the playing surface.  These rules will apply to the jump shot.)

Halfway Rule

Between the wicket just played and the next wicket in order is a line called the halfway line.  These lines are shown in the diagram above.  The lines, while not drawn on the court, will be defined by white stakes at the ends.

At the end of a turn in which a wicket is scored any ball which is resting beyond the halfway line for the next wicket is an offside ball.  The penalty for an offside ball is as follows:

1. The opponent of the player of an offside ball may direct that the ball be placed at one of the two penalty spots.

2. The penalty spots are located at points “a” and “b” at either end of the horizontal halfway line. (see diagram). 
3. The opponent decides which of the penalty spots is to be used.

A ball is not considered offside if it reached its position as a result of:

1. the stroke just played or

2. a stroke, wrong ball play or fault played or committed by an opponent or

3. contact with an opponents ball or

4. being directed to a penalty spot.

Scoring a wicket 

A wicket is scored by the ball passing through the wicket in the proper direction and in the proper order.  Scoring of the wicket is complete when the back side of the ball passes the plane on the playing side.  In the diagrams above with the ball traveling from left to right, drawing “A” is not a completed wicket.  In drawing “B” the wicket is complete.  The back side of the ball has passed the plane on the playing side even though it has not passed completely through the wicket.