[nestorD]

In my experience (I gave a demo as part of a talk today! It went great!), you want your code to be reliable (obviously... a 1 in 5 failure rate will bite you back on demo day), require as little thinking as possible (that can be worked around with increased automation, but if you automate all the things, you might as well be showing a recording), and rehearse things extensively (this applies to every part of a talk anyway).

[kevincox]

Also rehearse on a specific commit/build. I've seen so many cases where a feature or two were added since rehearsal and about was introduced into the demo path. If you do want to fix something for the demo run through your rehearsal another few times on the new commit.