anxiety public speaking

How can I overcome the anxiety of public speaking?
Whenever I know i hav a big presentation to do, my heart starts beating, my breath shortens, and sometimes I start to tremble and speak very quickly. and when I say "speaking in public:" I do not want to do a speech to hundreds – instead of 20, my classmates, the teacher. although there r only 5 ppl in a class and I'm ready for the task, like I did speak to PPL, Annex I of the above symptoms and even the stupidest of all the senses PPL my nervousness. this means – PPL thought who can not speak at all – that's me to a lesser extent in the presentation – the student teacher think ima strong, but there are also shy somethng wrong w me /? I thought that 3 years of high school I seem to overcome, but it did not – I think it's worse!
The problem is that your brain is a question between reality and fantasy. More smart people have this problem. People do not look too beast. Since you can not concentrate on one thing at a time, speaking in public causes your brain to think the terrible things that can happen to you while you 're up there, while at the same time, trying to focus on what you say. palaver is causing the problem. This same problem happens to people when they are afraid of heights. This height is usually the problem is the fantasy of what might happen to them. Focus the very fact contributes to this situation. I generally find that the more the crowd, the easier it is. One thing I found that contributes to the reality the situation is to choose a few people in the crowd and talk directly to them. Ask yourself, these people really want to be here? Are they really interested in what I say, or is the teacher who wants to know what I say. Analyze the situation before speaking. Knowledge of these activities can help bring things in perspective and to focus their attention on the reality of it all. Know your subject. This is the key to feeling comfortable. If you exude confidence, the public is intimidated. This may sound harsh, but I think this way and it will be useful. Practice your speech to your dog or your cat. Make sure you listen. If he nods to the head, doing things that you wake up. You'll be amazed how this helps, because when you start to rouse people, you think I should do to listen and will alleviate a lot of anxiety because that the brain will be transferred to the humor and the love she had for him the crowd. Good luck to you
public speaking=Anxiety