Start with what you know
A visible discarded tile is public information: one example of that tile has left a player’s concealed collection. An exposed group can also show information. These are facts; the intentions behind them are interpretations.
A beginner mistake is to read too much into one tile. A player might discard something because of a change in direction, a new draw or several other reasons. Be cautious about drawing conclusions from a single event.
Watch patterns, not just individual tiles
As a practice exercise, choose one suit and notice when examples of that suit appear. You do not need to memorize every tile on the table immediately. Following a smaller category makes the skill manageable.
Once you feel comfortable, widen your attention to honor tiles and exposed groupings. Experienced players often notice several different sources of information, but they developed this skill gradually.
Connect observations to your own decisions
Your current card tells you what you need for a candidate hand. Compare those needs with what is visible on the table. If many relevant pieces appear to be unavailable, it may be sensible to reconsider whether your plan is realistic.
Do not make the opposite mistake of assuming a tile must be available merely because you have not seen it. Other concealed racks contain information you do not possess.
Be respectful at the table
Some gatherings are casual and instructional; others are competitive. In a teaching game, a mentor may pause to explain an observation. During ordinary play, avoid announcing your interpretation of another player’s hidden strategy.
Discuss key decisions after the hand. Questions such as “What did that discard tell you?” invite useful learning without disrupting the current game.
This is independent educational information, not an official rulebook. For definitive American Mah Jongg play, consult your current official annual card and the rules used by your group.