Rummy is a game that requires understanding the table and your opponents' game because how you plan your game and play your moves depends on who you are up against.
A veteran player will usually use estimation as their rummy strategy to figure out what cards you have, as they tend to have a better understanding of the table including the open and closed decks compared to newcomers, who are often clueless about them.
Pay close attention to how your opponents are planning and playing their moves because you only have a few rounds to go before they have an estimate of your cards!
So, pick up cards from the open deck early on in the game, if they are useful to you, because once the game progresses, the only way to get desired cards will be from the closed deck: picking cards from the open deck later on is likely to reveal your strategy.
However, that’s not always the case, as we are all prone to making mistakes.
Things are easier while you're playing online rummy against comparatively less experienced players. Normally, an inexperienced player is mostly worried about their own cards only and often discards cards that you need, making your life a lot easier.
So, if your opponent is constantly discarding cards that you don’t need, you can safely assume that they are an expert player and they've estimated your hand. But if you are getting cards that you want, you are most likely up against a less experienced player who has no idea about your hand.
The level of mental fatigue is another crucial indicator that shows who you are up against. Therefore, when you are playing rummy, pay close attention to your opponent's moves.
Rummy requires a very high level of attention and experienced players are less likely to budge under pressure.
However, newcomers are more likely to make moves that may be considered an error of judgment.