What techniques should I use to teach my 5-year old to play chess?
I highly suggest taking him through the puzzles in Polgar's book. 

The book starts off with very simple chess problems, with only a handful of pieces, with the idea of "solve for checkmate in x moves".  The problems are designed with a logical progression, highlighting specific tactics and strategies, and become increasingly complex and demonstrating more advanced concepts that build upon lessons learned from earlier puzzles.  Polgar used the puzzles in this book to teach his daughters, who each became grandmaster players in their own right.