If you consult one of the major search engines, you will find that there a lots of people who claim to be experts in public speaking, and are eager to coach you. These people are expensive; the average fee is usually not less than 150 dollars per hour. So go for one of them only if you feel you really need this sort of thing for your career. Otherwise, if you are just a casual public speaker, or just want to impress your class or your friends or your town people, it is best to look up some tips on the internet and practice them on your own.
What these experts will do is simply take all the popular and traditional wisdom that we have about the art of public speaking, and package the whole thing into a methodical course using hi-tech gadgets, bells and whistles. And for the kind of money you shall be paying them, they will even hold your hands while they step you through it.
Public speaking has been an important art since the times of ancient Greece and Rome. It was a special branch of study in the ancient civilizations of Greece and Rome. As you perhaps know, many of the ancient city-states were democratic in nature, and their form of democracy was much more direct than what we can have in the modern world. Being small (by today's standards) habitations of a few thousand people, they were able to practice direct democracy, which means that the people were able to influence the government's policies directly, without there being any need for local representatives.
Those who wanted to be elected to the government, or to influence public opinion for a political purpose, had to be well versed in the art of public speaking, because they had to convince the people through open speeches delivered at a central clearing in the city, called the 'agora'. This branch of learning was known as 'rhetorics', and it was a very important part of a young man's (for women did not take part in politics in those days) education if he had any sort of ambition for high office.
So as you can imagine, public speaking is an art that has had the chance to develop over thousands of years. Do you imagine that your 150-dollar-an-hour expert, hired over the internet, can improve over that? They shall merely impart a modern polish to the whole thing, and liven it up with video recordings of your performance and computerized analysis. The basics are still just the same.
Sure, modern technology can help you lots if you're on a fast track to a seat in the senate. But if it's only for the school debating team, hold on to your dough. The traditional methods are still the best. Cicero or Demosthenes or Gladstone did not have computers, neither did they need one. Yet they were some of the greatest speakers in human history. Practice your tips in front of a mirror, like the way they did, and you'll be able to enthrall your audience and save money at the same time.