[Data collection fortnight ends today. And then we shall return to our regularly scheduled programming. Until then, here's Rule #1, from the archives.]

If you are giving a talk, or teaching a class, or are otherwise responsible for transmitting content from your brain to other peoples' brains, you should be able to give that talk - even if somewhat modified - without any visual aids. You should be perfectly capable of giving that talk, in the dark, if the power goes out. Because your science is so awesome that your words alone will make people revere you like the science god or goddess that you are.