I use the right-arm-out-for-a-right-turn technique. I've found that cars seem to be confused about the left arm bent at the elbow thing. If I'm POINTING in the bloomin' direction I intend to go, they get it.
Also, if I act like a car they treat me like a car. I hog the left half of a lane when I need to make a left turn, and haven't had anyone pass me on the right yet. If I'm wearing a big ol' goofy lime green jacket or a reflector vest I get even more respect. Like they trust me to behave appropriately if I'm gonna dress like such a total dork and ride in the road. Put a hot orange flag on me and I'm way groovy.
For the most part, I get treated like a slow car on my work commute.
And I always wave and mouth "thank you" to any car who gives me the right-of-way, even if it was legally mine in the first place. Public relations, dontcha know.
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson