I use double for everything except for quotes within quotes/within dialogue, where I use single. Like: "Bob's claiming you got drunk and kept yelling 'I am not the walrus' all last night," Alice said, raising an eyebrow. "What's up with that, Fred?"

I have no idea if that's proper, but it works. I don't really notice different systems as long as they stay consistent and dialogue has something around it. My eyes aren't the best in the world, and I easily skip around/get lost without some kind of dialogue indicator (or at least italics).

My personal quirk is always typing two spaces after a period. Never mind it doesn't even show in HTML unless you do dirty things with non-breaking spaces, I...can't stand not to.