Go to the IAmA sub-reddit: http://www.reddit.com/r/IAmA/
In order to post your thread you must “submit a link”. On the top right of the IAmA page, you can see three buttons, one of which is a blue button titled “Submit an AMA”. Or you can click here: http://www.reddit.com/r/IAmA/submit
Now you’ll need to fill out your thread.
TITLE: “Hi, I’m XXX. Ask me anything!” Feel free to elaborate and/or personalize.
TEXT: This is the additional content / information that redditors will see once they enter the thread. Include promotional information, more details about who you are, etc. This is also a good place to put your proof (please include a link to a Twitter page, an image with a sign saying “Hi” to reddit, a Facebook post link, etc.) More information on proof here.
Please don't use link shorteners here, the Reddit spam filter will remove your post.
Hit Submit, and you are ready to go!
The moderators suggest that you Submit your AMA no more than 15-30 minutes prior to your scheduled AMA time. This is more than enough time for redditors to start populating the thread with questions. Then, when you’re ready to start, you can jump right in to answering questions.
Go back to the new queue of the main IAmA sub-reddit page to see that your thread is live: http://www.reddit.com/r/IAmA/new
Click your live link thread when you’re ready to start answering questions. Hopefully there will be questions waiting for you.
When you see a question in the thread look directly below it and hit “reply”. That will allow you to answer that person’s question directly and your answer will fall directly below it.
Continue this process throughout the thread. You can answer whichever questions you’d like and you can ignore any that you don’t want to respond to.
Once you’ve completed your AMA you can hit the edit button underneath the intro text area to leave a sign-off message.