I gathered these bits strong players passed on to me over the years.Feel free to discuss and/or add your own.
Look at what's left on the board,not at what left the board
Always look at the most forcing move(s) first
When your opponent threatens something your first reaction should be: Can I ignore the threat?
When in doubt,move a piece out!
When stuck for ideas look for your worst placed piece and try to improve it's position
Never ever push a pawn "just because"
When up in material simplify.When behind complicate
Castle early (and often 😉 )
Doubled pawns are less of a problem when your opponent has no knights
In the endgame: when down in material try to exchange pawns,not pieces.When up in material try to trade pieces,not pawns
A dark square weakness is also a light square weakness!By placing your pawns and pieces on the dark squares you control,you attack your opponents pieces on the light squares
Never relax!Stay alert even when you're up a queen.Relaxing leads to sloppy play -> mistakes -> blundering away a nice win.
Study the endgame!It will improve every other aspect of your game because you will gain a better understanding of the strength and weakness of the various pieces
Enemy pawns and pieces that advance into your territory are easier to attack
Capture of the adverse king is the ultimate but not the first object of the game.
Tactics is what you do when there’s something to do. Strategy is what you do when there’s nothing to do.
The essence of planning is the visualization of a future position of some or all of your pieces.
The strategist plays by touch.
Opponents always have some kind of weakness in their position, even if imperceptible. Against that you have to play.
Make a plan that conforms to the position.
Take the initiative always on the side of the board on which one has more territory or greater fighting force.
Don’t move pawns where you are weaker.
Mobility creates its own plan.
Big edge, big plan.
Short-term plans pay best.
There are no good or bad pieces in the middlegame.
Worst piece first.
A bad plan is better than no plan at all.
A weak point is a square-not necessarily occupied-which can be attacked by heavy pieces.
Don’t drive away an advanced piece that is not hurting you. It will probably retire unassisted.
Strategically important points should be overprotected.
To get squares,ya gotta give squares.
An advantage in mobility means nothing unless it can be converted into something tangible.
Before making a pawn break, make sure your pieces are on their best squares. It is more important to frustrate your opponent’s strategy than to be obsessed with your own sly designs.
There is no such thing as an absolute freeing move.
When you don’t know what to do, wait for your opponent to get an idea. It’s sure to be bad.