Play the position from the other side of the board for ten seconds. What would you want to do if it were your move? Then stop that from happening. The word for it is prophylaxis, and it entered chess writing through Nimzowitsch, who built a chunk of My System around the idea.
7 
2 
a b c 
d f 
g Nothing about 1.h3 develops a piece or attacks anything. It is still an excellent move, because Black’s only comfortable way of getting the c8 bishop into the game has been taken away, and it can never come back. The bishop now has to settle for e6 or f5, where White is ready for it.
The everyday examples
You already play some of these without knowing the word.
h3 against a bishop that wants g4, or h6 for Black. a3 to stop a knight or a bishop landing on b4. Kh1 to step the king off the a7 to g1 diagonal before a piece appears on b6. And luft, the h-pawn push that makes a back-rank mate impossible, which is prophylaxis in its purest form: a move that stops something that has not happened yet.
Each one costs a tempo. Each one is worth it when the idea you are stopping is his best idea.
When it is worth a move
Not always. Prophylaxis costs time, and time is exactly what you should not be spending when the position is sharp or when you are already the one making the threats. If you have the initiative, keep it: a threat beats a precaution.
The moment to look for a prophylactic move is when the position is quiet and neither side has anything forcing. That is when most club players drift, push a random pawn, or shuffle a rook between b1 and c1. It is exactly the moment to ask what his plan is and remove it.
Build the habit backwards
At the end of each of your opponent’s moves, before you look at your own ideas, name his threat out loud in your head. Not a general feeling, a move: “he wants Ng4”, “he wants to double rooks on the c-file”.
Do that for a month and two things happen. You stop losing pieces to one-move threats, because you were looking at them anyway. And every so often you find a move like h3 that costs you nothing and quietly removes his entire plan from the board. The quiet move puzzles are the tactical version of the same skill: the winning move is the one that gives the opponent nothing to do.