I recently had to graph a family of devices using Cacti. Using templates was an absolute necessity so I spent time trying to figure out how to use them... It took me few days, so if I may spare that time to somebody else, I decided to write a little documentation on the subject. It's more a flow chart than anything else and it is not official documentation but it might help. Because the size of the flowchart is actually quite big, I only put a thumbsize image here but I included a link to a PDF version of the normal size one.
Link to the original post with PDF version of the document.
