Six wicket croquet is always played with four balls. Blue, Red, Black and Yellow. Blue and Black are considered partners as are Red and Yellow. If singles are being played, one player plays both Blue and Black while the other plays Red and Yellow. In doubles, one partner plays one of the partner balls and the other plays the other partner ball and they continue playing the same ball throughout the game. The colors are decided by a coin toss at the beginning of the game.
In American Rules, the balls play in strict rotation with Blue always playing first followed by Red, Black and Yellow. There is also "carryover" deadness. That is, once you have hit a ball (roqueted), you are considered dead on that ball and cannot hit it again until you have scored the next wicket (hoop) in order.
In Association Laws, the partner balls are the same, however, they do not have to plays in a specific order but each team does alternate turns. There is also no "carryover" deadness, that is, when your next turn begins, you are allowed to hit all of the balls again regardless whether you have scored your next hoop or not. There are other differences such as the starting of the game and the out of bounds but the games are very similar in the way that they are played.
Golf Croquet differs from both in that you are basically scoring one hoop at a time rather than having the ability to run the entire court. You cannot earn extra strokes (shots) as you can in the American or Association game.
In the American or Association game, you are able to run the entire court in one turn by what's called a "break". This is done by earning extra shots or "continuation shots". When a ball scores a "hoop", it gets one continuation shot. When a ball roquets (hits) another ball, it gets two more continuation shots and is called "ball in hand". The player then picks up his ball and places it in contact with the "roqueted ball". The first shot from this position is called the "croquet stroke" and then the next shot is the "continuation shot". Ideally, the player is able to get control of all four balls. He then has what is called a "four ball break" which makes it much easier to potentially run the entire court in one turn.
Croquet is a game of skill and strategy. Shot making is a critical part of the game. Hoop settings vary from 1/16" to 1/8" clearance. You have 'half rolls", "full rolls", "pass rolls" and 'stop shots", all techniques to control the ratios of the distance balls travel. It is indeed a game of precision and skill. These are all skills that are easy to learn but take a good deal of practice to perfect.
The strategic part of the game is also very important and can take much longer to perfect. Croquet has often been compared to a chess game on grass or perhaps a game of war. There offensive moves and defensive moves. Often an uninformed spectator has a difficult time understanding what is happening on the court. It can seem as though players are going everywhere else on the court rather than the hoop that they are for. All of this is usually in an effort to position themselves for the opportunity to gain the advantage. Basic strategy includes keeping your partner balls together while spreading your opponents far apart, forcing them to take long and difficult shots.
It is hardly the friendly backyard game that might have been played in Grandmother's yard where hitting a ball deep into the bushes was the most evil thing you could do. It can be a very serious game to those who play but at the same time offers a camaraderie that is hard to equal. It is a game for people of all ages and gender where the only advantage is experience.