Scanning: The First Habit of Every Solver
Learn cross-hatching, the quickest way to find easy placements in any Sudoku.
Scanning, sometimes called cross-hatching, is the technique you will use more than any other. It is simple, calming and surprisingly powerful.
How it works
Pick a digit, say 5. Look at every 5 already on the board. Each one rules out its row and its column. Now look at a 3×3 box with no 5 in it. If only one empty cell in that box is not ruled out, the 5 must go there.
Make it a rhythm
Work through digits 1 to 9 in order, then repeat. Many easy and medium puzzles can be solved with scanning alone. Treat it like breathing: steady and unhurried.