The subject is immense, and it's the typical case where the best strategy to start is buying a ton of books and studying. Second, practice endlessly. So I'll just give some random tips.
Preparation: you're not Steve Jobs
Steve Jobs prepared for weeks. And you and I are not Steve Jobs. So we need to prepare even longer.
The most important part in my experience is having an exceptional Keynote or PowerPoint presentation. To get there, you have to modify and redo it many times until you reach the essence of the message and every logical step is understandable to a six-year-old.
It's hard work. For my last hour-and-fifteen-minute speech, I worked 3 weeks on the presentation, some days 4 hours. The method is simple: create the presentation, run through it twice, note what feels off or requires too many concepts, fix it. Loop.
To prepare an 8-hour marketing course, I worked a year on the presentation. Remember: we're not Steve Jobs.
Slides: do the opposite of agencies
Slides help but should contain parallel, non-essential elements. So text at minimum or zero, basic charts, photos. My advice: take presentations from consulting agencies and senior directors and do exactly the opposite.
On stage: the show is you
The show is you. Attention goes on you. Feel it and seek it. Faking doesn't work. Feel your body follow your natural energy. Hands in pockets only for dramatic effect. Make lots of dramatic pauses. Create pathos. Animate. Make the audience vibrate. Engage them.
If you can, move through the audience. Walk back and forth, not side to side.
Responsibility is always yours
If the sound is bad, if there's no air, if there are room problems: it's your fault because you didn't ask the technicians in time. During one of my winter presentations in a large venue, I had the heating fan turned off because it was noisy. People were cold but they listened attentively. Your responsibility. Always and no matter what.
Jokes and authenticity
You need to be the type who can crack jokes. Don't force it if they don't come naturally. I tend to improvise only jokes: if they work, great; if not, so be it. You can compensate with body language for funny moments.
The real purpose
The purpose of public speaking is to generate change in people. When was the last time you tried to convince someone to do the right thing? If it's not in your nature, don't speak publicly. Seriously, you wouldn't be credible.
Because public speaking is scary and terrible. And simultaneously invigorating and one of the most gratifying experiences in life. Obviously, if you don't have an exceptional presentation, aren't prepared, and aren't naturally someone who tries to convince others, you'll only get the negative part.
Take a theater course. Practice in front of people. If you're not convinced of something, don't say it. You must care about your audience. You must have a low tolerance for boredom and clichés, otherwise you'll never be a good critic of your own work and you'll bore the audience like always happens in corporate meetings.
