How does one solve a Sudoku?

There is a only one correct solution (under normal conditions), but many ways those there leads. We would like to show here three possible variants, which can lead to success. As soon as one solved some mysteries, one uses its own proceeding. The basic rules for the solution of a Sudoku are completely simple: In each row, column and Unterquadrat the numbers may occur only once. Tap: One should write the number only into a field if one is sure that no other number can be inserted into this field; Sudoku is not called in vain "the only number".