Solving Sudoku : Nishio
One technique known as “Nishio” means to find a cell with just a couple of candidates, and to pick one of the candidates. If you work through from that point, and it turns out to be solvable and a valid grid, then great, you guessed right! If your guess was wrong, maybe it would show itself up within just a couple more moves, maybe it would take right until the very end before the last number was incompatible… Do you feel lucky? Some people will try just a few moves, before deleting them and trying another for speed.
Finding an incompatibility quickly means you can delete that option, and know that the other choice was correct. In some ways, picking the right number is less lucky, because you won’t be sure it was right until you’ve gone on to solve the entire grid!