"I will be showing the most basic to not so basic methods,trick and tips to finish a sudoku.this instructable is for anyone who plays or wants to play sudoku even if you don't know how to play. I'll start with the basic thing and progress to the less basic things.The objective is to fill a 9x9 grid so that each column, each row, and each of the nine 3x3 boxes (also called blocks or regions) contains the digits from 1 to 9. A cell is the smallest block in the game. A row , column and region consists of 9 cells and the whole game consists of 81 cells. A region has thicker lines surrounding it. This simply makes it easier to play the game.I most basic strategy to find missing numbers is scanning and it consists of 1)Cross-hatching. 2)Counting. 1) Crosshatching (shown in the first picture). You scan rows and columns to eliminate where a specific number can be in a given region.As you can see there is only one legal place left for the 1(marked green). 2)Counting. In counting you simply count all the different numbers that's in a row,column and region that connects to one cell. if there is just one number missing then thats what should be in the cell. Take a look at the second picture and see if you can figure out the missing number in the green cell. the correct answer is :4 legend: green = result red = cause(the cause of the result that is)"