I'd add to those the necessity to have some distance from the material to avoid the recency effect. You can have that distance either because you'll be talking

I'd add to those the necessity to have some distance from the material to avoid the recency effect. You can have that distance either because you'll be talking about something you haven't worked on for at least a couple of weeks, or because you've developed an ability to retain a birds eye view and adopt an outsider's perspective even when you're in the weeds. A lot of academic talks go wrong because, although the speaker deeply understands their topic, that teeny tiny detail that they were fiddling with yesterday is really not the thing they should try to communicate today, but they can't help themselves. Yet ask that same person to talk about their previous work, and you'll get a high quality impromptu introduction to the field.