Do speech and debate. You quickly get over that really quickly. Or if you are not of high school or college age start small. There are opportunies to speak publicly every day you just have too look for them. Most of your opportunities will either come in church, work, school, or around family. Next time there is an opportunity volunteer your self. Each time you do it, it wil become less and less like a chore and more and more natural.
-Former high school debate national champion and current college debate boss :) lol