Badminton Rules

The Basics

Badminton can be played either as a singles game or as a doubles game. All the equipment needed by the players are a racket each and a shuttlecock.

The Court

Badminton is played on a rectangular court that is 6.1m wide and 13.4m long. In a doubles match the full width of the court is used but in a singles match the width of the court is 5.18m. Marking lines down the length of the court indicate the boundaries for singles games.
There is a horizontal line near the net on either side of the court which indicates the start of the service area. In the centre of this line begins a vertical line that extends to the back of the court. This splits the service area into two boxes. At the back of the court are two horizontal lines which indicate the end of the service area. The closer one indicates the limit of the doubles service area, while the further one indicates the limit of the singles serving area
The 1.55m high net is hung over the centre of the court from stands on either side.
Badminton can be played outdoors but in the UK indoor courts are the norm. Any competitive event will also be held indoors.

The Game

Before the start of a match the players should toss a coin. The winner the coin toss can either opt to serve or choose which side of the court to play on. Once they have decided, the loser takes the discarded option.

Scoring

In a badminton match players aim to win the best of three games, each of which is played to 21 points. Each time a side wins a rally they receive a point and the right to serve for the next point. The first to 21 points wins the game.
Like sets in tennis, games must be won with a two-point lead. If a game is tied at 20-20, the game continues until one side achieves a two-point lead or until one side scores 30 points (30-29 is an acceptable score for victory).

Serving

To serve in badminton the server must hit the base of the shuttlecock in a single stroke with their racket pointing downward. Neither the server nor the receiver can lift a foot off the ground until the shuttlecock has been served. The shuttlecock has to be below the server’s waist (defined as the lowest rib of the server) when it makes contact with their racket.
The shuttlecock must make it past the receiver’s service line and stay withing the court boundaries, otherwise the serve is a fault, resulting in a point being awarded to the receiver and service passing to them. There are no double faults in badminton.
In a singles match the player serving serves from the right if their score is even and from the left if their score is odd. The receiving player stands in the court box diagonally opposite to him. The server changes sides for each serve. The receiving player cannot come forward of the service area
In doubles the server stays the same throughout the game and follows the same pattern. If the opposing team wins, the player on the right serves if their score is even and the player on the left serves if their score is odd. When a team is receiving, the player diagonally opposite the player must stay in the serving area. The other player can stand anywhere they like on their half of the court so long as they don’t distract the server. The same is true for the non-serving player in the serving team.
By tradition, in a mixed doubles game the serving team’s female player will make the first serve of the match

The Game

The shuttlecock must make it over the service line when it is served, otherwise it is a fault and the receiving team wins both a point and the serve.
After the serve a rally can take place anywhere within the court boundaries and a point is scored when the shuttlecock hits the ground within these boundaries. If the servers win the point they continue to serve. If the receivers win the point they become the servers.
If the shuttlecock lands outside the court boundaries this is a fault and a point goes to the receiver. Similarly if a player fails to get the shuttlecock over the net this is also a fault. It is also classed as a fault if the shuttlecock hits the ceiling.
The shuttlecock can only be hit once in a rally. Though only the base can be hit in the serve, the feathers of the shuttlecock can be hit during a rally.

Let

Rallies can be replayed if something disturbs its flow, for example, people wandering across the court or anything landing on the court. This is known as a let. In a competitive match these will be at the umpire’s discretion, and in a friendly game at the player’s discretion.
If one player serves before the receiver is deemed ready an umpire may give a let and ask the server to replay the serve. This cannot happen if the receiver returns the serve.
Source--talkbadminton