Did you know that it only takes about 3 seconds for people to pass judgement on you when they meet you? There are tons of different non-verbal factors that come into play here (I'll keep you guessing and save them for future posts). The factor I'd like to look at today is your posture.
Remember that people judge you from the minute they see you, not the minute you step on stage or to the front of the boardroom. Begin preparing yourself for your talk before you enter the room you'll be speaking in.
Push your shoulders back, raise your chin, pull in that belly and stick out that chest. It's amazing how when you look confident you also feel more confident. Enter the room like you own the place. You have every right to be there. Everyone who is there is there because they want to hear what you have to say. Your thoughts and words are important. Your posture should also show that!
In addition, proper posture will help you with your breathing and voice projection during your talk. By standing up straight with your chin slightly higher than horizontal you are actually opening up your airway. This is important for voice projection since your voice travels on your exhaling breath. You need to be able to take a nice deep breath and use your diaphragm to push that air out again.