The first thing you need to do is write some jokes. Read my article "How to Write Hilarious Jokes" for helpful tips on doing this.
Find an open mic comedy night in your area. To find a place to perform, browse a local entertainment magazine. Or type "open mic comedy [your city]" in your favorite search engine. If you have no luck there, go to Chucklemonkey.com - they have open mic listings in all 50 states.
Before performing, visit the venue, watch a show, and introduce yourself to the other comedians. Let them know you want to perform stand up comedy for your first time. Schedule a date from one to two weeks away.
Invite your friends, family, co-workers, and anyone else you think would be interested in watching a comedy show. Use social networking sites like MySpace and Facebook to announce your show.
Rehearse your jokes so you have them memorized by the time you set foot on stage.
Now the date has finally arrived for your performance. Bring a camcorder or an audio recorder to record your set if you can. Also, keep a list of your jokes in your back pocket just in case you get stage fright and forget them.
When it's your turn to go on stage, go up there and give it your best shot. It's a scary experience, but don't worry - the other comedians and your audience are on your side! When the person running the show "gives you the light", you usually have one minute to wrap it up. Tell your last joke and then exit to your applause!
Congratulations - you did it! Whether you did great, bombed, or anywhere in between, you should be proud of yourself for having the guts to do stand up comedy. Have a drink, you deserve it!
Get other comedians' contact information and ask about other shows in your area. They will be able to tell you about other places you can perform.
If you recorded your set, watch/listen to your performance. See if you can make any improvements for next time.