Using side rope and adjusted gun technique.
Witches hats (cones) are set up to show the angles. This is the most heavily viewed video in my collection.
23.4mb wmv
http://www.palmtreeservices.com.au/video/sidelean.wmv
Post 11 below has some demonstrations of piecuts which shows leaving wedge or pie shaped hinges has little influence on felling direction.
Training style vid - felling a side leaner, most viewed video in my collection