Development
DEFINITION
Bringing your pieces — especially knights and bishops — off their starting squares to active squares where they contribute to the game, rather than leaving them undeveloped while other pieces move repeatedly.
Why It Matters
CircleChess's analysis found that moving the same piece multiple times before completing development is the single most commonly broken opening principle — it happens in 54% of beginner games. A simple coaching drill: after each of the first eight moves, count how many new pieces have joined the game.