Rehearse
Again and again and again. So you know every detail of your talk, all the slides and the order in which they appear. Practice in front of a mirror or even video yourself. This is the best way to find potential tripping points, inconsistencies, and also gives you a chance to weed out the crap jokes.
But more importantly, it will make you so comfortable with the content that you won’t need notes or prompts and you’ll appear conversational but knowledgeable.