Constant habit of mind checking for enemy threats.
Why it matters
Prophylactic thinking is the habit, not the move: every turn, before choosing, you look at the position from the other side and ask what they want.
It costs a few seconds and it removes most blunders. Almost every piece dropped in a normal game was taken by a move the player never asked about, because they were busy with their own idea.
See it on a board
Nothing is hanging and no attack is under way. h3 costs one move, gives the king a square, and takes every back-rank trick off the board for the rest of the game.
Checked: the position really has the feature described.
How to play it
- After the opponent moves, say out loud what that move threatens. Every time, including when it looks harmless.
- Before you move, ask what you would play if you were them.
- If you cannot see a threat, spend the move on your worst-placed piece or on your own king's safety.
At each level
The same idea, said the way it is taught at each age.
Bishop · ages 5–7
After every move your opponent makes, say what it attacks. Doing that every single turn stops most blunders.
King · ages 10 and up
At a higher level the question changes from 'what is threatened' to 'what do they want in five moves'. The answer is what to prevent.
What goes wrong
- Checking only for captures, and missing the quiet move that sets up a real threat.
- Asking the question after choosing a move instead of before, which turns it into justification rather than checking.
Questions people ask
- Does this slow my play down too much?
- It is faster overall. One question per move takes seconds; recovering from a dropped piece takes the rest of the game, and usually does not work.