All of the above really. Personally I seldom (ever?) present on a topic I'm unfamiliar with, so I don't "research from scratch" just for a presentation. [1] I

All of the above really. Personally I seldom (ever?) present on a topic I'm unfamiliar with, so I don't "research from scratch" just for a presentation. [1] I will research though some finer points just to check that what I "know" is accurate and up to date. Perhaps more along the lines of fact-checking than research. [1] a colleague once had 2 weeks notice to do a 4 hour training session about a subject he didn't know to replace a presenter who got denied entry by border control. That was very stressful for him, but he delivered well...