One thing that I have learned about public speaking, or even just persuasive speaking, which I think falls into psychological.
When talking about something, you need to own your space. You can do this in many ways, but the best way to get people to listen to what you say is to own the space around you. Show confidence, show that you're comfortable. Convince others ‘I am so sure what I'm saying is awesome and true that I am not in the least bit nervous about this speech.’
Walking around is one way to do it. Use up all of the stage. Move. Lean down, stand up, walk to the front, walk to the back. Just be careful not to overdo it, otherwise it might seem more like fidgeting which will have the opposite effect.
Open yourself up. Spread your shoulders, lift your head, widen your stance. Uncrossed legs, relaxed stance, chin up, shoulders back. This is how you want to look.
Another small tip is to achieve the ‘I know what I'm talking about’ effect is to bring a drink with you. It shows you're calm, allows you to take a little rest, pauses show that you're thinking about what you're saying. Depending on the drink, it can also show confidence in of itself. I always take a crystal glass with me wherever I go and fill it with just spring water. Never use a bottle or a plastic/paper cup. A clear crystal glass projects a good professional outlook.