Self-confidence is a very important thing a public
The first step in achieving such self-efficacy is changing the way you think. Start thinking positively. People who have a low self-confidence are the ones who think 'low' of themselves. Control your views about yourself and accentuate the positive. Being optimistic would likewise help. Remember, whatever you perceived yourself to be, it will come to life. If you think of yourself as a very timid and shy person, then you will be one. If you consider yourself someone who has this so called 'stage fright,' then you will surely have that kind of fear, and will never be able to confidently speak in public. If you are awfully afraid to commit mistakes, then you will definitely make a ton of them. Try foreseeing yourself appropriately dressed up, comfortably standing behind a lectern with a microphone properly held in your hand, uttering the words correctly within the right tone and volume of voice, and executing significant gestures with your other hand in front of a crowd that is so attentive, convinced, and satisfied. You are the master of your thoughts, steer it in a way that would help you be confident and successful.
Then after you have set your mind into thinking only the positive things, think about what is important to you and what your goal is. Once you have discovered what is important to you and set a specific goal in achieving it, you will be inspired or motivated to take action and better yourself. Your speaking assignment is important; therefore your aim is to successfully finish it with a resounding applause or perhaps a standing ovation from your audience. That is more important than the obstacles hindering you from a well-delivered speech -- fear, shyness, nervousness, or low self-confidence.
Now, realize your strengths and capabilities; look back to your achievements. Highlight your strengths. Perhaps it would help if you jot down all the things you have accomplished, the successes you have earned, be it very small or great ones. It could be a medal or trophy from high school, or as simple as a 'good job' from a teacher or a friend. Write down the good qualities in you; the things other people say you are good at. It could be in the field of sports, culinary, music, leadership, time management, housekeeping, gardening, teaching, or as simple as making friends. Note it all down and you will be surprised how long your list would be.
After you have undergone these steps, you should be ready to commit yourself to success. Obligate your self that you will confidently stand out there and deliver your speech like there is no tomorrow. Do this with willingness. Forcing your self to commit will not help. To be more exciting, try orally promising to yourself in front of the mirror that you will do your part with the best of your abilities. Take this promise to your heart and always bear it in your mind and you will be successful. Good luck!