A friend about to give her first keynote speech asked my advice on how to approach it, then suggested I post the advice for others to see. So here it is:

1. Keynote content has a large burden. Ideally it provides context — or at least controversy — for the rest of the event. It should have big ideas of where we’ve been or where we’re going, but also be grounded in the practical in a way that makes it relevant to attendees. It isn’t very difficult to strike this balance, but probably different topically from what we do day-to-day, so give yourself extra time for research and imagining.
2. The keynote speaker also becomes an implicit ambassador of the event. While some may board their private jet immediately following the talk, I found that I felt I should continue the keynoter persona throughout the event, answering questions and socializing with everyone, including the organizers.