I think it's fair to say that most presentations are not rehearsed properly.
In fact, I know that many speakers don't even bother to practice their presentation out loud.
It is this lack of preparation that leads to so many mediocre presentations.
Why is rehearsal so important?
When you don't rehearse, you are essentially delivering a draft. Would you ever write a business email without proof reading it first? Of course not. The same goes for a presentation. You really have no idea what your presentation is like until you deliver it out loud.
And when I say rehearse, I don't mean going through it in your head or muttering through parts of it driving in the car. Proper rehearsal means standing stall and delivering it out loud as you plan to on the day. Whether you practice to your spouse, your cat or a blank wall. You have to deliver it at full volume all the way through.
A surprising thing happens when you practice your presentation out loud. You will suddenly identify sentences and phrases that sound completely wrong, even though they look fine on paper. That's because they way we write is vastly different to the way we talk. When we write we are free to use long sentences with multiple clauses. When we write we are often more formal and elaborate than when we talk.
All of this makes you look like your putting on a front and takes away from your authenticity.
Study any good speech and you will find that they are peppered with short punchy sentences. Simple language that doesn't look inspiring on the page but resonates when delivered from the stage.
The number one way to rehearse
The only way to rehearse properly is to get out a camera and record yourself. There's really no excuse not to. Today you will a find a camera on your phone, your laptop and your iPad.
Is it painful watching yourself speak on camera? Yes it is until you get used to it. But it's a whole lot less painful than wasting the time of your audience because you were boring or hard to follow!