What are the middle game principles? What are the middle game principles? I have already seen numerous principles regarding the opening and ending, but not the middle.
1 - Centralize and coordinate your pieces. This is when tactical opportunities will begin to materialize.

2 - When your position is cramped, exchange pieces.

3 - When ahead in material, exchange pieces, not pawns.

4 - When you have a bad or inactive piece, exchange it.

5 - Don't launch an attack on the flank until the centre is secure.

6 - When the opponent's king is exposed, look for tactics and combinations.

7 - When the opponent's development is poor, look for tactics and combinations.

8 - Attack your opponent's weak and backwards pawns.

9 - Occupy your opponent's weak squares. Knights are particularly good at establishing outposts.

10 - Don't make unnecessary pawn moves in front of your king. This weakens your position.