- Always survey the full grid before placing your first digit
- Start with the most-constrained units — rows, columns, or boxes with the most givens
- Cross-hatch each digit 1–9 across the boxes before turning to individual cells
- Place all "forced" digits (only-one-option cells) before starting pencil marks
- A strong start creates a cascade — each placed digit enables several more
Why Your Starting Sequence Matters
Sudoku rewards efficiency. The order in which you find cells does not change the final solution, but it does determine how quickly the puzzle opens up. A strong start gives you a cascade of easy placements early, which fills in candidates automatically and reveals the harder patterns sooner.
Step 1: Count the Givens Per Unit
Before placing anything, scan every row, column, and box and mentally note which ones have the most givens already filled in. A row with 7 given digits only needs 2 more. A box with 6 givens still has 3 empty cells. Start with the fullest units — they have the fewest possible placements and are easiest to complete.
Step 2: Cross-Hatch Digit by Digit
Pick the digit that appears most often in the givens. For each of the nine boxes, check which rows and columns already contain that digit — those eliminate cells within the box. If only one cell in the box is left for that digit, place it.
Work through all nine digits this way, starting with the most common ones. On Easy and Medium puzzles, this cross-hatching phase often fills 15–25 cells before you need any pencil marks.
Step 3: Fill Obvious Singles
After cross-hatching, some cells will have their last empty slot forced. If a row has 8 digits and one empty cell, the missing digit goes there automatically. Fill all of these Naked Singles before moving on.
Step 4: Start Pencil Marks
Only after the obvious placements are exhausted should you start writing candidate notes. At this point, many cells will have only 2–3 candidates rather than the original 9, which makes the notes cleaner and the patterns easier to spot.
Common Starting Mistakes to Avoid
- Starting with the emptiest area. The corner with 6 blank cells looks like a good start — but it has fewer constraints, so it is actually harder. Go to the fullest area first.
- Adding pencil marks immediately. Filling in all 81 cells' candidates before placing any givens creates a cluttered grid. Earn the easy placements first, then add marks only where needed.
- Working randomly. Jumping between unrelated cells wastes time. Systematic digit-by-digit cross-hatching is faster than picking cells at random.
For a full walkthrough of the solving process, see how to play. Ready to practice the right starting sequence? Open a free puzzle and try it now.