How to be confident in public-speaking?

Yup, dressing up comfortably and decent will rise up your confident. Try practice speech in front on the mirror... When you done with it, and you felt that you had gain some confidence. Try practice in front of your bro or parents.. If they smile or they laugh at you, do nothing, Just look in their eye and smile, and continue. Lets nothing stop you. when you're doing presantion, the most important things is your eye contact with all the listeners, you wont have to stare at all of them. just look across them and have more eye contact to the important ppl. Dont make unnecessary gesture, stand comfortably and hands in front and SMILE. its ok if thy doesn't listen, You could always ask relevent questions to interact with the listeners and have their attention. Adding in some humour( not jokes) into your presentation will be a credit too. JUST REMEMBER, when you think that you're beautiful, you will be. Dont get work out by guessing what other ppl might tot of you (negatively) Just fill up yourself with "yourself" not anyone else.You'll be good, I'll wishes you WELL DONE in advance .. ^^

Just keep reminding yourself something very important, something to live by even.
"Everyone else can go blow themselves because I'm bad as f-ck."

practice. years of practice will teach you public speaking. its a skill you have to learn and only by experiences does it truly get easier. Preparing yourself physically and mentally is one of the steps, its where you start.