I've found that people in general will veer towards the sound or the direction you state you are passing them. I've also noticed that in general no matter what you do you will piss off half the people you pass regardless of your attempts to politely tell them your intentions.
My preferred method is to just ride on by. By the time they realize I'm there I'm gone. I do say hello, have a great ride as I pass.
This occurs on the roads. I don't ride MUTS, etc.

There are no specific rules...just what is made up by people...