Finishing a logic puzzle without wiping the board

Mark the squares that are certain, leave the uncertain ones blank, and never fill a row that still has two possibilities.

Logic puzzles usually fail because the board gets filled too fast. A square that seems 'probably right' is a square you will have to erase later, and erasing one square tends to break three conclusions stacked on top of it.

The discipline that works: fill only squares that are certain, mark uncertain ones with a temporary symbol, and never fill a row that still has two possibilities. If a row has two possibilities, every deduction below it also has two, which means nothing has actually been proven yet.

When you are stuck, go back to the tightest constraint rather than the emptiest square. Tight constraints look like a short row, a small region, or a number with only one legal position. That is where the next move lives, almost every time.

I use only two marks: a dot for definitely not this, and a small letter for maybe this. There is no third mark, because every extra mark has to be remembered, and remembered marks can be wrong.

If a board has run past twenty minutes with no progress, save it and walk away. Logic puzzles often resolve faster after a break, because the mind stops repeating the same assumption.