(Because I know somebody will inevitably link to it, here's Michael Beirut on why "educating" clients is patronising bullshit: http://jonsandruck.com/i-?-michael-bierut/ . I respectfully disagree. I love working with clients that are interested to learn why a particular design decision is in their best interests. I don't think you need to leave your client feeling stupid, but being able to refer to existing research to back up your opinion? Yeah, that's handy).