Areivim, Kapusta and Ames, thanks for the feedback. I strongly believe in the smiling part. When I say to be confident, it doesn’t mean that you think you are the President of the USA. Just that you have some area or interest or hobby (or even taste in clothing) that makes you feel good about yourself, and is infectious.
The same holds true with public speaking. When first starting to speak, some people worry for days about what the others will think, and what if I forget, and I am so nervous and all kinds of things. This itself will ruin the speech.
You need to get up there and speak to the crowd like you are speaking to your friends about something that really excites you. Tell some jokes and keep them guessing. You need to be confident that you are entertaining them (even if it is an educational talk). Stop focusing on yourself, and focus on interacting with the crowd like they are your best friends. Then everyone has a good time. You need to open up to the world around you, instead of thinking everyone is judging you. It is hard to explain this concept, but once it clicks, then you can have the crowd eating out of your hands, and public speaking will never be the same to you, and will be fun, instead. It is all about confidence. It doesn’t mean you are the biggest world expert, it just means you are comfortable and relaxed with what you want to say.