Retaining valuable cards for extended periods of time is a typical error made by rummy players. High-value cards can be helpful in building runs and sets, butop 50 rummy app listt they can also add to your hand's point total if a player is eliminated before you are. Card Discardment: Take Care. Discarding cards that could be advantageous to your opponents is another frequent error. To prevent giving your opponents an advantage, it's critical to carefully consider which cards to discard.