I find that many of our guests are not only non-sailors, they are non-boaters. The Admiral seems to have an unending group of people that "always wanted to go sailing", so let me add a few things.

7. Explain/warn your guests before you do anything that makes a noise. The pre-start engine alarms, clearing out of the slip/channel horn blowing, etc. We like to minimize fear on board.
8. Pre-boarding. Selection of footwear and clothing needed to keep warm/cool/dry. We have had everything BUT boating suitable shoes including stilettos. Tiny sundresses are stylish for sure, but a little revealing when moving about the boat.
9. I hate to bring this up, but what do they do if they feel seasick or get seasick? We have had people get queasy tied to the dock.
10. Depending on the length of the charter it may be a good idea to give the talk about respecting personal space, picking up after yourself and good hygiene(the stinky talk).
11. What would you like the guests to do while under way, what would you like them NOT to do. Many of ours feel like they should prove themselves to be useful while on board.