Here is a step-by-step guide on how to play Gin Rummy:

1. Number of Players: Gin Rummy is played with two players.

2. Cards: Use a standard 52-card deck with no jokers.

3. Deal: Each player is dealt 10 cards. The remaining cards form the stockpile, with the top card turned face-up to start the discard pile.

4. Objective: The goal is to form combinations ("melds") of cards in your hand, by either:

   • Sets: 3 or 4 cards of the same rank (e.g., three 7s).
   • Runs: 3 or more consecutive cards of the same suit (e.g., 4, 5, 6 of Hearts). Cards not in melds are "deadwood" and have point values (Aces=1, face cards=10, others = face value).

5. Turns: On your turn, draw one card from either the stockpile or the discard pile, then discard one card.

6. Going Out: You can end the round by:

   • Going Gin: Forming melds with all your cards (no deadwood). This scores 25 points plus the opponent's deadwood points.
   • Knocking: If your deadwood points are 10 or less, you may knock to end the round. You score the difference between your deadwood and your opponent’s after they lay off cards to your melds.

7. Scoring: Score points based on the deadwood difference after a player goes out. The first to reach 100 or 250 points (set before the game) wins.

8. Additional Rules:

   • The first player to act may take the top discard card if they want.
   • Opponents can reduce their deadwood by adding cards to your melds after you knock (laying off).
   • If the knocker’s deadwood is not less than the opponent’s, the opponent scores a 25-point undercut bonus plus the difference.

This summary covers the core rules to get started playing Gin Rummy. The game involves strategy in choosing when to knock and which cards to keep or discard to minimize deadwood and maximize points.