1. Being Boring. Speaking in front of a group of people is as much about entertaining as it is about informing, sharing facts, or explaining. For some reason, most public speakers are entirely oblivious to this truth. They seem to think that if they plow ahead and bury the audience with words that they are communicating. For the five things you must do to actually communicate with an audience, see my earlier article called Public Speaking According to Old MacDonald.
2. Failure to Use Illustrations/Examples. This is the biggest reason speakers are boring. And by illustrations, I do not mean pictures and graphs on PowerPoint. I mean stories and colorations to bring your point(s) to life. Remember this: you haven't told them until you've shown them. I suffered through a sermon recently that was devoid of even one single example or illustration. If you can't (or don't, or worse, won't) come up with memorable sketches, illustrations, stories, and humorous little ditties to help bring your points to life, you are dead before you begin. Keep your seat when they introduce you. At least that way the audience will remember you.
3. Being Nervous. Okay, telling you not to be nervous is like saying don't have a headache when you do. Still, like a headache, there are things you can do to prevent them and even things you can do to mitigate their symptoms once you have one. The way to prevent nervousness is to practice your presentation a million times, even if it's just to your spouse who is wearing headphones and watching Youtube videos the whole time. Practice your talk until you're sick of it and you won't be as nervous. The other thing to do is give enough talks in front of people often enough that you no longer get nervous. I promise this will happen.
4. Not Credible. 76.5% of people agree that there is nothing worse in the whole world in our entire human existence than a speaker who over-exaggerates, makes unsustainable claims, and plays fast and loose with statistics. Stay away from statements such as "best in the world," "greatest ever," and words such as "unbelievable" and "awesome." If it's unbelievable, then why are you trying to get them to believe it? And awesome should be reserved for something that truly invokes awe, such as, say, the Creator of the universe.
5. Using Power Point. The only thing I can think of that makes me shudder more than having to sit through a Power Point presentation is reading through the entire U.S. Tax Code. Twice. Oh, and having a dog lick the inside of my mouth. I would bet there are more people who've butchered presentations using Power Point than there are teenagers who've typed "LOL" into a smart phone. Power Point is like a gun, perfect for what it's designed for but deadly in the hands of someone who doesn't know how to use it. So how can/do you use Power Point properly? Use no more than 10 slides and have no more than 10 words on each. If you actually read the text that comes up on the slides to the audience, you need to quit public speaking altogether and get a job writing U.S. Tax Code.
6. Going On Too Long. Rambling is only okay if you're a Jeep. Have something to say, say it in an entertaining and memorable way, then shut up and sit down. The cluelessness of speakers who go long is only akin to that of left lane drivers. Know how much time you've been given and stay well within it. The trick is to be done a few moments before the audience wants you to. This leaves them wanting more, which is good. Why would you want to leave them wanting less?
There's more, but if everybody who ever held a microphone in front of a group would only implement these six things, the world would be a better place.
The next time you are trapped in a boring speech that is going on too long with some dweeb reading teeny tiny text on a Power Point slide, remember this article and send it to them anonymously. Consider it an act of public service.