Round three of my first junior tournament, and I had a rook on d1, a queen on d2 and a decision I had not finished making. Two fingers landed on the rook. Then I saw that it was the queen that wanted to go to d8, and by then my opponent, who was nine, was already saying the word that every child in that hall knew. Rook it was. I lost the game and I have never touched a piece early again.
Touching a piece with the intention of moving it is choosing it. That is Article 4.3 of the FIDE Laws of Chess, and it is the single biggest difference between the game on your phone and the game in a hall.
Your piece, their piece, one of each
Three cases, and they cover everything.
Touch one of your own pieces and you must move it, provided it has a legal move (Art. 4.3.1). It is the first piece you touched that binds you, not the last one, so brushing the knight on the way to the bishop is the knight.
Touch one of your opponent’s pieces and you must capture it, provided some capture of it is legal (Art. 4.3.2). This one catches the players who like to pick an enemy piece up and look at it.
Touch one of each and you must capture their piece with your piece (Art. 4.3.3). If that particular capture is illegal, you fall back on the first piece you touched. And if the two of you cannot agree which came first, the Laws assume it was your own piece, which is a small mercy.
None of this needs you to lift anything. A finger resting on the top of the king is a touch. Straightening a rook without saying anything first is a touch. The word the article uses is intention, so a sleeve across the board is not.
Then comes the second half of Art. 4. The move is made when your hand releases the piece (Art. 4.7), and after that the square is settled. It is completed when you press the clock (Art. 6.2.1). Between those two moments there is a real gap, and it has one official use: it is when a draw offer is supposed to be made.
When touching costs you nothing
Art. 4.5 is the escape clause: if none of the pieces you touched can be moved or captured legally, you may play any legal move you like. The usual version is a piece that is pinned to its own king.
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h 1 The same applies to a rook boxed in behind its own pieces or a bishop with no square. Test it in your head before you panic: if the piece genuinely cannot move, no claim against you can stand.
One more piece of small print, and it is the one that decides arguments. Art. 4.8 says you give up the right to complain about your opponent’s touch the moment you touch a piece yourself with the intention of moving. Claim first, play second. Not the other way round.
King and rook, in the wrong order
Castling has its own rules inside Art. 4.4, and beginners hit both of them.
Touch the king and the rook, and you must castle on that side if castling is legal (Art. 4.4.1). Touch the rook first and then the king, and you may not castle on that side this move; the rook is the piece you touched, so the rook has to move (Art. 4.4.2).
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d e h 1 There is a third case. If you touch the king intending to castle but castling on that side turns out to be illegal, you must make some other legal king move; if the king has no legal move at all, you are free to play anything (Art. 4.4.3). All of which is why the order is king first, every time, with one hand (Art. 4.1): lift the king to g1, then swing the rook to f1. There is a page on which piece you move first when castling and it is worth two minutes of your life.
Promotion works the same way. Your choice of piece is fixed as soon as the new piece touches the promotion square (Art. 4.4.4), so decide between the queen and the knight before your hand leaves the box.
What the arbiter actually does
Usually nothing, because nobody called them.
Touch-move is claimed, not policed. One arbiter is looking after forty boards and will not have seen your hand. So the procedure is yours: stop the clock, put your hand up, and wait without arguing across the table. The arbiter asks both players what happened, and where there is no evidence either way the move on the board tends to stand. If a player simply refuses to comply, Art. 12.9 gives the arbiter a ladder that runs from a warning through adding time to the opponent all the way to declaring the game lost.
Say j’adoube before you touch anything you only want to straighten, and say it while your hand is still in your lap. There is a whole page on that word, because saying it afterwards is worth nothing.
The habit that fixes all of this takes about a week to build. Hands in your lap. Pick the move, then check what your opponent does about it, and only then reach out. Strong players look slow and casual at the board; what they are really doing is keeping their fingers away from the pieces until the thinking is finished, which is the same discipline that stops most blunders before they reach the board.