Millions of people suffer from the effects of stage fright everyday. Whether it's in the workplace, a wedding or any event that has people speaking in front of groups chances are a great deal of those speakers are internally crippled with fear. There are groups like Toastmasters that train you to be a better public speaker but they take months and cost a lot.
One simple tip that has helped many people and is fast, free and easy to try is a quick change in your mental perspective. What I mean by this is, rather than think of yourself as speaking to a group, give yourself the mindset that you are speaking to individuals. If you have to talk on a certain topic for several minutes, mentally address the group individually focusing your eyes and attention on one person at a time for 20 to 30 seconds. Just casually move your attention around the room rather than trying to address the whole group at once. You will be amazed at how well this works. You don't need pills, you don't need to be drunk and often times this simple change in how you view the speech you are about to give can make a world of difference in how confident you are.
Visualize yourself just having a simple conversation with a friend over coffee or on the phone. If you are going to talk to your friend about a car you are thinking of buying you wouldn't try and memorize your speech before hand you would just talk about the subject that you know casually and without fear. Take the same attitude into your next meeting or presentation and you will come off as more intelligent, better prepared, and more confident than you ever have before.
You are not, being judged by a group of 20 cynical people. You are simply having a one-on-one talk with individuals moving your eyes and attention around the room from person to person as you speak. There is really no difference to doing this than there is to having a simple conversation with your friend about your plans for the weekend. The more you refocus the better you will get and soon you'll be giving presentations like a pro.