If you mean forums, then no, you don't ask to become a moderator/admin, we pick people we think will make a decent mod/admin when we decide we need more staff. People just asking is annoying.
If you mean front site though, then feel free to look in the Site Staff forum and browse the threads there, and help out with creating pages/graphics/whatever needs to be done, and after a while, if the senior site staff people think you're good enough, they might consider making you part of the front site staff.
