Distilled from many years of public speaking experience, here is a collection of ideas that help make a great speaker.
The most important point. If people are straining to hear you they will switch off and it doesn't matter how good the talk itself is. Don't turn to look at your slides while talking: if you're talking you should be looking at the audience to avoid drops in volume. If using a hand held microphone, hold it against your chin: this usually gives you the correct volume level and also means that as you turn your head, the mike stays with you, again avoiding drop outs.
Be entertaining / engaging
Your talk should be an enjoyable audience experience. With so many demands on their time, you should leave them feeling glad that they chose to spend an hour listening to you. As a speaker you've only used one hour of your time, but you have the potential to waste 100s of hours of others' time. Make sure you don't.
Have a clear aim
Talks should have a single aim. "An assessment of climate change adaptations", "Why the Grand Canyon is so special", "How volcanoes impact a region", are all clear aims that will guide you in designing the talk and help ensure you stay focused.
Audiences warm to a speaker who seems nice. They are more prepared to go along with you for the journey you are proposing to take them on, and it makes for a splendid social lubricant. Smile and make it appear you're glad to be there.
Never underestimate the audience’s intelligence…
People who come to talks are intelligent and well motivated. They love being surprised, and being given new insights they weren't expecting. But...
…you must make your world accessible to them
No matter how intelligent the audience, you must build bridges with your words and images to help make it easy for them to enter and understand the world you are trying to introduce them to. You may well be an expert in your field but that alone does not mean you can provide a good talk. Don’t rely on your expertise in the subject alone. You need the wit and imagination to be able to introduce it to someone who may not have the capability to follow what you're saying just yet, but will do if you present the information well. Suddenly, they will feel cleverer, and thank you for opening their eyes to a new world.
Use visual aids to support your talk (if possible)
Whatever the audience is looking at should help them engage with your words. We are visual animals and well chosen illustrations or artefacts can make life much easier for the audience. I've used ropes, inflatable boats, and climbing equipment to bring a talk alive and help the audience relate to what I'm talking about.
PowerPoint slides are cheap: don't skimp on them
Early in my career I was booked by a company who'd hired a TV celebrity and author the month before to talk about a topic ideally suited to visual imagery. They'd droned on, reading from a script, for 90 minutes and used only two slides. The audience was unimpressed and the company swore never to book them again. Slides should support or illustrate the point you are making: this helps the audience follow you. Don't keep the same slide up long after it's ceased to relate to what you are now talking about.
So, you've created a beautiful slide with maybe 3 or 4 images on it and some explanatory text. Looks great on your computer screen doesn't it, where you can pore over it, close up, like a printed document? Trouble is, when you use it in your talk, people toward the back of the room won't be able to see the images clearly or read the text. It doesn't matter how good the slide looks to you at your desk, always look at it from the audience's perspective. Too many images on your slide? Give them a slide each, where they can be displayed at a good size for an audience. Text on your slide? Make it big so people aren't squinting, or worse, giving up trying to read it. Hard to fit all that big text onto the slide now? Spread it out over several slides. You have no excuse if people complain they can't see what's on your slide. Four slides in your presentation cost you no more than one slide: they're not rationed.
Create a story, or series of mini–stories / themes
Too often I've attended a talk where the images have been fantastic but there has been nothing connecting them. If you're giving a talk you are a storyteller, no matter how good your images may be. The images should serve the talk. I have some beautiful images that will never appear in any of my talks, because they don't illustrate what I wish to talk about. Which brings me to my next point...
Have something to say
Research your subject thoroughly. If a country, make contacts before you set off: this will help you decide what images and information you need to collect, and increases the chance that you will have meaningful experiences that people will want to hear. What intrigues you most about the country? The people? The landscape? The environment? Engage with your topic, gain some unusual insights, and you will have something to say.
Get the audience to care
Get them to care about the people in your slides, about you, about the subject, anything. Engage the audience's empathy and they are with you and want to follow you on your speaking 'journey'.
'The world belongs to the enthusiast who keeps cool'
Wise words from William McFee. Enthusiasm is good, but only takes you so far. An enthusiastic speaker, who also presents a well planned, well illustrated talk, will always be appreciated.
The end result
The audience feel glad they entrusted you with their time. Their minds are abuzz with the insights you have given them and they feel they have been given new perspectives they wouldn’t otherwise have acquired. Worlds have collided fruitfully.