Enter the speaker coach.
Now, everyone seems to have their own idea of what a speaker coach should be; as far as I'm concerned, a good technical speaker coach should be able to do two things:
- Critique the mechanics of your presentation style, and
- Evaluate the technical content of the presentation itself.
The latter focus--the technical content--should be evaluated in the context of the intended audience. If you're targeting your presentation to beginners, the question is, "Did they get from [nothing] to [basic understanding]?"; presentations to folks with intermediate skills should result in the listener "getting to the next level," and speaking to advanced audiences...well, at that point it's usually about bringing something new to the table, since they (by definition) already know the beginning and intermediate stuff, right? So, you want to find someone who fits the "typical attendee" model, NOT someone who already knows the material.
Long story short, folks - find a person (or persons) who can do these two things for you. Take them through your presentation. Don't stop, don't pay any attention to the fact that there are only one or two people in the room, and don't hold anything back: give the presentation as you expect to deliver it on stage. If you can get a projector, do so; make this as realistic a "dry run" as possible. After you're done, sit down with them and ask two questions:
- "Could you hear and understand my words and how I spoke?"
- "What can you tell me about [subject of presentation]?"
I can't say this strongly enough: DO THIS. DO THIS SEVERAL TIMES. Every runthrough you can make before hitting the stage will improve your performance.
Now, go practice!