I have had the great good fortune to enjoy two long-running, concurrent careers. I am about to celebrate 40 years as a professional cabaret performer and actor with performances in Austin and Dallas, and I recently completed 36 years in the A/E/C industry, most of them as a marketer.
In my 40 years as a professional performer, I have probably spent more than 15,000 hours in front of audiences—ranging from small (6 or 7 people) to very large (more than 3,000 people).
As an A/E/C marketer, my in-person audiences have been considerably smaller—from 3 or 4 in a meeting up to as many as 75-80 people in a conference session.
I have found a lot of similarities between the two professions, in both the preparation and presentation phases.
In the preparation phase of both, you learn the material. As a cabaret performer, this means memorizing the words; I don't believe any song is ready to go in front of an audience until it is memorized. And since I often accompany myself, this means learning the the piano part as well.
As a professional A/E/C presenter, the preparation phase does not entail memorization, but it does require that you know the material well enough that an interruption does not leave you drawing a blank, unable to go on. And to have a back-up plan if your projector's bulb burns out.
Final preparation happens right before you go "onstage." This is the warm-up. As a singer, I warm up my voice. If I am standing up (someone else accompanying), I also warm up my body. I make sure every joint is loose, that muscles are warmed up and flexible, that my joints are not going to crack when I move, and that my ankles are ready for any step (or mis-step) I might take.
I do an abbreviated physical warm-up for professional presentations, usually in the hall outside the conference room. It helps me control how my body moves and makes me very confident on my feet. I don't lose my balance even if I'm wearing new shoes and standing on a slick floor.
With solid preparation, you enter the performance phase confident enough to get over any hurdle. For example, many years ago, working a club in Austin, TX, we lost lights and the sound system for about 30 minutes. Not wanting people to get up and leave (I do like a full tip jar!), I had the waitresses bring a half-dozen lit candles to the piano so I could see the keys, and continued to sing until power was restored. Nobody left the club!
This equates to having your PowerPoint fail during your short-list presentation. You must kknow the material well enough to keep the presentation going even with no visuals, unless the client asks you to stop.
If you have good material and you have prepared well, you will not need to read your music or your slides. Instead, you will be making eye contact with your audience, connecting with them and actually communicating the message of your song or presentation, not just putting out information.
You will know from their facial expressions and body language if they "got it" or got lost somewhere. And you will be prepared to deal with either eventuality.