After loosing 20 games or so to my son (feels like 50 games), he has offered some tips for me:
The four squares in the center are the most important part of the board. If you can’t control the light squares, lock in the dark squares (or vice versa).
Make plans and carry them out
This could mean simply short term goals or long term goals. Try to see what your opponent’s intentions are BEFORE forming your own. This is a critical part of chess.
Evaluate your own weaknesses FIRST, and then spot your opponent’s weakness.
Always consider your pawn structure when playing. Evaluate if your pawn structure is good or bad. Do you have isolated or doubled pawns? How can you avoid that beforehand
Good and Bad Bishops
Determine your Good Bishop and Bad Bishop based on pawn structure. Do that for your opponent as well when trading pieces.
Determine whether a trade is good or bad (or perhaps just okay) based on this.