Personally I've never found a single guide that you could hand to someone, but if you're coming from a background of HTML and CSS then you should pick up formatting rules pretty quickly - they're essentially the same, but implemented via a GUI rather than explicitly specified selectors and tags. The key for me is to just pretend that none of the explicit styling options exist - so no use of Bold/Italic/Centered/Whatever buttons, and instead turn on the styles pane and apply all formatting from there.