When you rehearse, leave plenty of time for honest feedback from a skilled presenter.
As the presenter, we get too familiar with (and attached to) our ideas. You may think you’re making each point more clearly and persuasively than you really are. So ask a skilled presenter to give you honest feedback. Give her a printout of your slides and have her jot down what you say well, what you don’t, what’s essential to keep, and what’s distracting. She might say things like, “When you put it that way, people won’t be able to follow you,” and, “That term sounds derogatory to me,” and, “I thought you expressed it better last time, when you said…” The extra set of eyes and ears helps you see and hear yourself the way the audience will.