Though no official rules actually exist, these are the most commonly used Rummy rules.
The Players
Rummy may be played by 2 to 6 players and uses a standard playing card deck of 52 cards. The game can be played for a round, a number of rounds or to a target score agreed upon before the start of play.
The Deal
The first dealer is chosen at random. Or, it can be decided by each player drawing a single card from the deck, with the lowest card getting to deal first. The number of cards dealt is dependent on the number of players detailed below.
2 Players 10 cards each
3 to 4 Players 7 cards each
5 to 6 Players 6 cards each
If there are just two players, the deal alternates. If there are more than two players, the deal moves clockwise around the table. Starting with the player to his left, the dealer deals the cards one at a time to each player until all players have the required number of cards. The dealer places the remaining cards face down on the table to become the stock. He then turns over the top card and places it face up to the right of the stock to start the discard pile. Once the cards have been dealt, the players can then examine and sort their cards. The player to the left of the dealer takes the first turn.
The Objective
The object of the game is to dispose of all your cards. This can be accomplished in one of three ways after the initial draw:
Drawing (Mandatory)
Each player must begin their turn by either drawing a single card from the top of the stock pile, or taking the top card from the discard pile. If you draw from the stock pile, you add the card to your hand without showing it to the other players. If the stock pile runs out, the top card from the discard pile is set aside and the remainder of the discard pile is shuffled and turned face down to become the new stock pile. The top card then starts the new discard pile.
Discarding (Mandatory)
Each player must end their turn by discarding one card from his hand face up on the discard pile. Once the player has discarded, his turn is over and he may not play any cards again until the turn moves back to him.
Melding (Optional)
Cards may be grouped by placing approved combinations (aka melds) of three or more cards from your hand face up on the table before you. Alternatively, you may choose to keep melds in your hand for reasons of strategy and/or the chance to gain a bonus.
Card Combinations
There are two kinds of combinations, Runs and Sets.
A Run is three or more cards of the same suit in sequence
A Set is three or four cards of the same rank in different suits
Ending the Hand
The player wins the hand by being the first to play all the cards in their hand by either melding, laying-off or discarding. Once a player has gone out, the hand is ended. No other players may meld, lay-off or discard their cards even if they have valid combinations already in their hand.
Scoring
At the end of the hand, each player adds up the points of the cards remaining in their hand as follows: The King, Queen and Jack are worth 10 points each. Number cards are worth their face value. Aces are low in this game and worth 1 point each.
Going Out
A player "goes out" when he gets rid of all his cards and he therefore wins the game. If all his remaining cards are melded, he may lay them down without discarding a card to end his last turn. This ends the game and there is no further play.
Going Rummy
A player "goes Rummy" when he disposes of all the cards in his hand in one turn and goes out without previously having put down melds or laid off any cards against existing melds that have already been placed. When this happens, every other player earns him twice the amount of points they would ordinarily owe.
Optional Rules
1. You may only lay down one meld during a turn
2. A player cannot lay off any cards unless they have put down at least one meld
3. If you draw from the discard pile you cannot discard the same card in the same turn
4. The game ends when the stock pile runs out with players then scoring the value of the cards left in their hand
5. In order to go out, you must end your turn by discarding your last card
6. Values in the hand at the end of the round are added to the player’s own score as a penalty. In that case, the player with the lowest score at the end of the specified number of rounds or when the target score is reached is the winner.