How do you get rid of stage fright?

Give yourself a physical anchor onstage, meaning pick someTHING on the set, or on your costume, and everytime you feel the butterflies rising, physically touch that thing. It will simply ground you, and give you a sense of familiarity and comfort. It can be anything, like a button on your sleeve, or a coffee mug on a table, but actually put your hand on it, take a breath, and keep going. If you get nervous again, repeat. It's completely mind-over-matter, but it's always worked for me.
Oh, I realize now, that you may not even be an actor but maybe are asking from the point of view of a musician, or public speaker.but I'd imagine the idea would still be the same. I'm an actor, so that's where my mind automatically went.

Practice your speech in front of a mirror and when you are talking just imagine everyone in their underwear.

Works great!

Just imagine yourself naked in the middle of a high school classroom, with the bully that always picked on you barreling down holding a bucket of pig's blood.

No wait don't do that.

You can't get rid of the butterflies in your stomach, but you can get them to fly in formation.

Learn to experience (and welcome) the physical manifestations of anticipation as excitement, rather than anxiety and fear. Are you new to speaking/performing in public? Practice makes...practiced performance, and creates experience and memory. What venue, or audience do you appear in front of? Have you looked into Toastmasters? An idea: practice being your ideal loving, approving, compassionate and supportive audience member: go to other live events and be that person for the performers. Then clone yourself and carry that person with you to your performance and have them in the audience.

don't look directly at the crowed

RE: don't look directly at the crowed

With all due respect, I have to disagree. Having a rule like that can really mess you up if you accidently turn the wrong way and find yourself facing the audience (crowd). Besides, like the solution to "don't think of an elephant" is to think of a giraffe, the solution to not facing the crowd is to find a face in the crowd and play to them.

I agree with practice make prefect. Knowing what your doing will help ease the nerves abit. And also remember we all learn the most when things don’t go as prefect as we planned. So just jump in there.