A couple of years ago I had a conversation with another blogger (I think it was Jeff Sypeck, but memory fades), in which he related an earlier talk with other scholars about how they didn't know how to do the kind of public outreach I was doing. He said, as I recall, "It's not some big mystery; you just do it!"
The more I think about it, though, it's easy to do, but hard to do well. One of my goals has long been not just to do popular outreach myself, but to encourage others too. Eventually, I'd like to see a whole army of Professors Awesome out there interacting with popular medievalists.
So, to that end, I present to you a guide on how to be a Professor Awesome, PhD.
First, you might need an attitude adjustment. I think medieval scholars have a better attitude about this than most, but there's still some snobbiness. As one scholar said to me recently, "What a waste of time!" These folks like to present themselves as casting pearls before swine. Dude, don't be a jackass. You aren't all that important -- hence the pompous schtick in the double-title "Professor Awesome, PhD." I promise if you ever get to be sooooo important that your time shouldn't be wasted on the plebs who are interested in your scholarship, I'll let you know.
Learn who your audience is. Someone who comes off the street to a public lecture you're giving at your school, local library, book club, or some convention isn't going to be an idiot. They don't have a specialist's knowledge, but they're smart and want to know more. I think the average would be like a motivated sophomore in a survey course -- they are smart and eager, but don't yet have any background. Sometimes they have a bit of background, but it has faded since they left school.
Simplify, but don't condescend. Probably the hardest line to walk is how much to simplify things. Leave all your jargon back at the office. Never "interrogate" a subject, "consider" it. Talk about "world-views" rather than "paradigms." Assume they've heard of any canonical texts you're talking about, but they either haven't read them or read them so long ago that they can't remember it. One of my favorite ways to handle this is to call for a refresher, e.g. "I know most of us read at least part of The Canterbury Tales in school, but let me refresh your memories" -- then you can give lots of details without saying, "Hey, you're stupid, and I'm going to treat you that way."
Emphasize the fun stuff. Unlike your students, they don't have to be there, so sex it up a little. If I'm talking about The Saga of the Volsungs, I'll make a joke about french kissing a wolf. If I'm doing The Prose Edda, I'll point out the passage where Tolkien gets his dwarf names. If I'm talking about "The Dream of the Rood," I'll make comparisons between the depiction of Christ there and professional wrestlers. Remember all the fun stuff that drew YOU to medieval studies? Share that with your audience.
Involve the audience. If there's some kind of activity you can do, do it. For example, if I have to do The Decameron, I do my trauma exercise. At the very least, leave copious amounts of time for Q&A -- my general rule of thumb is to always have twice as much time for Q&A as I spend talking. They don't just want to hear, they want to be involved -- so let them.
Use any AV equipment at your disposal. Make PowerPoint presentations, but don't let them be bullet points. Instead, if you're talking about the Crusades, have an image of a crusader, or a map showing major battles of that particular crusade, or whatever. The role of AV here is similar to the role of the over-the-shoulder graphic on TV news -- meant more to illustrate than explain. Of course, if you must use a long quote (which I discourage), always put the text up so they can read along. There's no need to overload the audience with information; after all, there won't be a test later.
Above all, try to have fun. Just as dogs (supposedly) sense fear, audiences sense when you're not enjoying yourself. Bring the joy of medievalism to them!