"Remember, a nice person with a gun makes guns nice for everyone. A jerk with a pistol makes guns seem scary. "
- Kevin from Exurbanleague
One of the biggest rules of open carry IMO is "don't be an asshole*." In fact, that's a pretty damn good rule to live by, open carry or not.
*Note that some folks are going to see you as an asshole no matter how you act, how polite you are, or what you do. There's nothing you can do about such folks except be yourself and be the better man.
Like it or not you are an ambassador for the cause when you OC. If you're a rude, abrasive asshat you do more harm than good. As my mother said after the first few times I OC'd around her in public "people respond well to you."
First impressions and politeness go a long way. If you're already that way, then then it's an asset when you OC because people who interact with you walk away thinking "that guy with the gun on his hip was a nice young man." Frankly, there are so many things that people seem not to bother with these days that I've always been taught were just common decency. Helping people who obviously need it, holding the door for the person behind you, bothering to say "thank you" and "excuse me."