Empathize. This is something I didn't get right away, then Hope pointed me in the direction of the Center for Nonviolent Communication, and their parenting advice. It's simple. Put yourself in the child's shoes. See things from their point of view. This might not change the rules (i.e. "You still can't run through the parking lot, and you still have to hold my hand."), but it can inform your response in a given situation. Verbalize it ("I know you want to run and it upsets you that you can't"), and you validate the child's feelings even if it doesn't change what they can or can't do.
Explain. This may be a reaction to my own upbringing, where unquestioning obedience was the rule and "Because I said so," was the end of any further inquiry. Growing up, I found it insulting because it seemed to indicate that you either (a) didn't have a good reason for something or (b) didn't think I was capable of understanding it. Kids understand more than they're often given credit for. Explanation doesn't mean argument, and it doesn't mean that you negotiate away authority. (i.e. "You can't run through the parking lot by yourself, because there are a lot of cars here, and you can get hut of one hits you.") Again, it's validation of the child's personhood so that he'll validate his personhood, and include in it a right to legitimately question authority. Of course, that's assuming you believe that authority should be questioned and can be questioned legitimately.
Listen. Contrary to how I was raised, I think children should also be heard. I'll listen to Parker even though it doesn't always mean he gets his way. (i.e. "I know you want cookies, but you need to eat some dinner first.") And sometimes I end up realizing what he's really asking for or trying to say. Listening logically goes with the two previous bits. It can help teach a child to express himself appropriately and affectively, and build important lines of communication that will be crucial later on.
Anyway, that's all I got in the way of advice. At least right now, anyway. To me, those three things are the difference between being an authoritative parent versus an authoritarian parent. The first one being what I'm aiming for.