Most of my clients want to be coached and trained in public speaking delivery, especially body language and voice. They are happy to receive any type of training in that area and they find it fun. But when it comes to feedback on the content of their presentations or speeches they seem to hold back a little. I believe that, while delivery is key, content is much more important for reducing your public speaking anxiety. Good content is well-thought of and rehearsed. It becomes a part of you. Well-prepared content proves to you and others that you know what you are talking about. By not taking your content seriously, the usual speaker's anxiety (that we all get) will get worse.
Back in the time when public speaking was all about speeches, speakers took a long time to brainstorm what they wanted to say. They would take months or even weeks to ponder on the kind of things they wanted to express, and then carefully choose the words, images, metaphors and structure to implement. They had the awareness that their speech was very much anchored in the present. It had to do something to the audience. It could not be reproduced in any other way, nor recorded or tweeted. You had your chance and you went for it. It was almost ceremonial. Speeches were created through a combination of actual writing and multiple rehearsals. Speakers practiced saying their speeches so they could get used to their own voice and memorise the speech at the same time.
Today, many presenters rely on visual aids and documents such as PowerPoint. They use their slides as their life boats. They claim there is little time or need to prepare each speech by writing it out, let alone to rehearse it by saying it aloud. They are therefore not giving enough though to their content. Your best life-boat is the confidence that your content is relevant, engaging and that you know it well. Then, and only then, you can learn how to deliver it well.