When playing Gin Rummy strategy is a key concept. It is important that players remember that there are 52 possible 3 card melds of 3 of a kind, for example, 6 of Hearts, 6 of Spade and 6 of Diamonds. And 44 possible 3 card melds of the same suit, for example, 3 of Clubs, 4 of Clubs, 5 of Clubs. There are more chances to form 3 card meld of 3 of a kind.
It is advisable to draw cards from the stock pile than from the discard pile, unless the card in the discard pile completes a Set or a Run immediately. Otherwise, you will be hinting the cards you need to the opponent. This will stop the opponent from discarding cards that would help you.
It is good to memorize the cards that have been discarded to know the chances of completing Sets and Runs in your own hand. For example, if you have 2 Kings and if you notice the third King was discarded earlier in the game, it is dangerous to retain these cards any longer as it has high point value which will work against you. Discard cards that will not help your opponent. You should analyze the cards that would be useful to your opponent by memorizing the cards your opponent picks up from the discard pile. Do not discard cards of the same suit or number as your opponent's previous discard as it may be of use to your opponent. For example, if your opponent discards a King of Diamond and you have an unmatched King of Hearts in your hand, do not discard this unmatched card as your opponent might need this King of Hearts to complete a meld.
Middle cards are more important than face cards or high point cards as they can be used to make more Sets and Runs. 7 is the most valuable card in the deck. It is easier to extend a sequence using 7 than any other card. Hence, do not discard a 7 as it will give the opponent a better chance to create a sequence.
It is good to delay discarding the high valued deadwood cards or 2 sequence cards to prevent your opponent from making high valued melds. If you have high valued sequence cards or unmatched cards in hand, do not discard them before half the stock pile is used as it may be of value to your opponent. Besides, you may find a combination in the middle of the stock pile. However, after reaching half deck, if you still did not find a match, it is advisable to discard these cards in such a way that your opponent's chances of knocking or melding does not get higher.
If you suspect your opponent might knock soon, draw a low valued card from the discard pile and discard a high value deadwood card. This way, you can minimize your deadwood cards total value.
Try and knock early.
After knocking, if you have a choice to attach a card to a Run or Set, prefer to attach the card to a Set than a Run. This will prevent your opponent from attaching their deadwood cards to your meld.