Once your priority in front of any group is to be with your listeners in Relational Presence, specific content gets much easier to plan. Here's an article about how to open and structure a masterful talk. Below I expand on the all-important first 30 seconds, the ideal opportunity to establish a sustainable relationship with your audience.
After being introduced, the first mistake most speakers make is to start to talk the moment the applause ends. The second mistake is to open with a joke, a provocative statement, or a social nicety.
Establishing a sustainable relationship calls for at least one full breath (no less than 10 seconds) of silence after the applause ends, to honor the moment, the occasion, and your listeners. (Not the technique of a "pregnant pause," but an authentically transparent receptivity that allows everyone in the room to arrive, including you.)
Then, an opening line most likely to bring the room to rapt attention is a sentence that sets up a one-minute story of an "aha!" turning point moment from your life. That sentence wants to be delivered conversationally, clearly, not dramatized, with precisely enough information to allow your listeners to visualize a scene (as in a movie) where the action is just about to start.
Then another full breath (yes, another 10 seconds) that signals everyone (including yourself) to make the pilgrimage to that moment. This 3-part "hello" (breath, sentence, breath) determines your first impression. When you master this 30-second dance, your capacity for what is called "public speaking" will fall into place beyond your wildest dreams.
Do read the article linked above for the rest of the opening sequence and structure of an effective talk. Here is an example of the real world power of such an opening. Twenty-five years ago I was at a networking meeting where the featured 10-minute speaker, a CPA, opened like this:
"[Full breath] When I was a child, most nights I would hear my parents arguing loudly well into the night. [Full breath] I would calm myself by counting sheep, imagining numbers on their sides. The numbers would go into the thousands, so I grew up with a sense of relaxation around large numbers. Eventually I became an accountant, and I love to relax my clients around their numbers."
I was not the only one in the room attracted to work with this man who was far from dynamic, but transparently real. He became my accountant for 15 years, then my financial adviser when he shifted careers.
So what's your story?