All you have to do is click "contact us" at the bottom of the page and write them that you want to be a moderator! There's no xper requirement, though you should have a good reputation as far as answers go, intelligent, helpful answers and not much joking or sarcasm or rudeness. Other than that, best of luck to ya!
You just email the admin and tell them you want to be a moderator. You don't have to have a certain amount of points but they do look into your history on the site before "hiring" you. A mod or admin would probably be better able to explain how the process works but I think its pretty simple if you are relatively active on this site and give good responses to questions.
Contact the admins, and tell them you want to become a moderator