So where do you start? The goal of Sudoku is to fill in a 9x9 grid with numbers so that each column, row, and 3x3 section contain the digits between 1 to 9. At the beginning of the game, the 9x9 grid will have some of the squares filled in. Your job is to use logic and fill in the missing digits and complete the grid. Don't forget, a move is incorrect if, any row contains more than one of the same number from 1 to 9. Any column contains more than one of the same number from 1 to 9, and any 3x3 grid contains more than one of the same number from 1 to 9.
Always look for rows, columns of 3x3 sections that contain 5 or more numbers, this is the best place to start. Then start working your way through the remaining empty cells, trying the numbers that have not been used. In many cases, you will find numbers that can only be placed in one position considering the other numbers that are already in its row, column, and 3x3 grid. Clear as mud? To visually simplify things try breaking up the grid up into 3 columns and 3 rows. This means each large column will have 3, 3x3 grids and each row will have 3, 3x3 grids. Now, look for columns or grids that have 2 of the same number. Logically, there must be a 3rd copy of the same number in the only remaining 9-cell section. Look at each of the remaining 9 positions and see if you can find the location of the missing number.