"I'm just not good at public speaking," I hear people say as they're preparing for a business presentation. "That's fine," I tell them, "since I don't want you to make a speech." A business presentation is not a public speech. It's not theater. You don't need to get every sentence delivered perfectly. Um, I'd even add, it's okay, if you say, "um", and other so-called filler words, because, the more naturally you speak the more authentic you'll sound to the listener. And it's authentic speakers who come across as the most credible, believable and ultimately, often, the most persuasive.
If you were asked what you did last night, you wouldn't need to memorize any notes or strain to read the bullet points on your PowerPoint to respond. Because you know what you did last night. That's why the best preparation for your presentation is knowing what you want to tell your listeners. And by that I don't mean the specific words or sentences you want to say.
The first part of preparing for any presentation is thinking about the last part: the moment you've finished speaking. How do you want the audience to feel after they've listened to you? What do you want them to do? Change their opinion? Hire you? Buy something?
Then go backwards: What do you need to convince them of to think or act in that way? Make a list of your key points. Never write them out word for word. Delivering a memorized speech is about the worst way that anyone is going to come across as an authentic speaker. It's a useful technique for performing Shakespeare but otherwise nothing works more against a successful business presentation than memorizing what you want to say. And just writing out sentences is often the first misstep. Even if you don't memorize the words, you may be tempted to subconsciously try remembering how great it sounded when you did write it out.
Instead make your list using bulleted shorthand. Write a few words for each key point you want to make. If you need more than a few words, that may be a sign you should spend your preparation time learning more about the subject so you feel confident on the topic rather than memorizing. Mastering your subject matter is also going to make you much more effective if you get asked questions. Memorization works fine for the theater since actors don't get interrupted or interrogated about what they just said.
Yes it can be a problem when the number of "ums" grow to the point of distracting your listeners from what you're trying to get across. The way you--or any other speaker--is going to be most authentic is to sound like you know what you're talking about. Yes, effective delivery is important and how you say your words can be as important--or more important--than the words themselves. But it's in sounding confident and genuine that you're going to have the greatest impact on your audience. So know as much as you can about what you're presenting about and, um, don't worry if you say "um!"