Know your last line. You don't need a scripted first line or middle but it needs to be obvious when you're done, so finish strong, know what your last words will be and spend the whole time moving towards them.
I said slow down and I meant it, but also: vary your speed, tone, and volume. It's boring to listen to someone speak at the same speed for more than half a minute or so. Speed up as you are gathering momentum in a point or argument or illustration for example.
Speaking of varying speed and pitch and volume: you often command more attention by going quiet than you do by going loud. For emphasis, drop your volume a little, and drop your speed at the same time. People will lean in.
Use the geography of the space, whether that means walking around a stage or standing at a podium or whatever. Return to specific places in the room or postures to make related points. Lean or step forward to create intimacy. Lean or step backward to create formal distance.
Be emotionally honest. If you're saying something you don't have any feelings about why are you even saying it? And if you do have feelings then let them show. That goes for an academic talk as much as a dramatic monologue.
@thatpaul I hesitated to boost this earlier as I liked that the Favourites were coming organically, but I also want to share this thread because there are some really good #PublicSpeaking tips in there