Hi Alex,
i recently attended a presentation by an experienced postdoc. She got so nervous she had to stop in the middle of it and leave the room so it isn't just new students that get nervous. My advice is to practice your talk well before hand. Beleive that you are the person present who knows the most about what you are talking about. Also realise that the audience don't know what you intend to say, if you miss a bit out or say things in the wrong order they don't know! Remember to breath deeply too.