As a passtime, I enjoy solving Sudoku puzzles. Over the years I have developed a way of solving even the hardest, level 13, ones. I call it the Serpentine technique.
The technique is explained in a series of Powerpoint slides that can be dowloaded using the link below.
I will update the slides from time to time as new techniques are discovered.
A printable pdf worksheet for use with this technique can also be downloaded here.
Your comments and suggestions are, of course, welcome.
Rational-Understanding.com 