Theres 1 more trick :d someone told me just picture everyone in their underwear that makes you feel more comfortable..he he lolz just kidding. Be confident, You should know what your speaking about do not mug up your topic.Jus maintain a good flow,be clear.See how the crowd responds,if they are yawning means its getting boring and you have to try to get their attention,speak up to the point the dont beat around the bush.Dont be nervous and even if you are pretend you are confident.And if you make mistakes dont stop and wonder why you did it,instead say sorry and go on from where you made the mistake,or the other option is to pretend you never made mistake and go on.Just stand stall and feel right!!!