This! It's one of the most important thing to remember – people paid money and came to listen here, and you've been invited as a speaker, so that means that you have something important to tell, and people really want you to succeed.

I also recommend a fantastic book on the topic by head of TED conferences, Chris Anderson - "The Official TED Guide to Public Speaking". It helped me immensely when I was preparing to my first big public speaking event.

Agreed! As I wrote to a comment elsewhere on this page: "Most of the time, they selected your talk based on their interest in the contents (and less so on your delivery), and so they want to learn a thing or two. They will be graceful towards your presentation (style, delivery, slides) if at the end they got what they came for: you sharing data, knowledge, insights or wisdom. You don't want [to make] that too difficult for them, so you should work hard on improving your presentation delivery, but sharing knowledge is appreciated over sharing jokes or just well-designed slides."