Sudoku - Logical Shape Puzzle

The classic puzzle game Sudoku first appeared in the US in the 70s of XX century.
Sudoku invented based on the «Carré latin» ancient games (Latin Quarter), invented in the XVIII century by Leonhard Euler.
Sudoku playfield is a large square with the dimensions 9 x 9 cells, which in turn is divided into smaller square field size of 3 x 3 cells.
One of the most effective ways of playing Sudoku can call this approach:
Record the number in the top left corner of the square cell, and then cross out illegal according to the rules of the game the number of the cell.
Play Sudoku better slowly, thinking through options for different numbers.