Distilled from many years of public speaking experience, here is a collection of ideas that help make a great speaker.
An obvious but important point that some speakers overlook. On numerous occasions I've had audience members come up to me after a talk to specifically thank me for having a clear voice. If people are straining to hear you they will switch off and it doesn't matter how good the talk itself is.
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 leave home and 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 100's 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. If using slides, they 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. We are visual animals and well chosen images or illustrations can make life much easier for the audience. 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.
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 the country or 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 politics? 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.