Catdoku
Sudoku games
Fill a number grid using the clues already on the board. In standard Sudoku, each row, column and three-by-three box contains the digits 1 through 9 without repetition.
2 games
Start with forced placements
Scan a nearly complete row, column or box and check its missing digits against crossing constraints. A number belongs in a cell only when the rules support it, not because the position looks promising.
Use notes deliberately
If your chosen version supports notes, keep possible digits up to date after each placement. Look for a digit that has only one possible position in a region before guessing.