Hi Everyone,
The sole candidate technique (also called naked-single) is one of the simplest techniques, and you are possibly using it without even realising.
Basically:
When all the other possibilities for the sudoku cell have been removed, and only one choice remains - then it must be the correct value.
Check out this example:
As you can see, if you follow the 3 rules of sudoku, then there is only one possibility for the green square:
The numbers 1 to 9 must occur only once;
In each row (knocks out 3,9,7).
In each column (knocks out 4,5,8)
In each 3x3 block (knocks out 1 and 2)
So the only number left (the sole candidate) is 6.
Cheers
Gath