Requirements / process to become a shuttle astronaut?

Hi guys,

I'm a long time lurker, first time poster, and I finally have a
question that warrants my registering for DejaNews .. *ahem* I mean
"Google Groups."

What are generally the minimum requirements to become an astronaut on
the shuttle? In my case, I'd probably be looking at mission
specialist, since I'm going to school for engineering. What level of
education is necessary – masters, doctorate? Does military experience
help (I've been contemplating the Navy Nuclear OCP for post-grad)?
Are there any particular fields of study career paths that are more
favorable than others? After one has attained the necessary
qualifications, how does he apply, and is it better to wait until
after becoming highly qualified, or to begin application as soon as is
feasibly possible? What percentage of applicants are actually
accepted? A lot questions, I know, but I never managed to let go of
the typical ten-year-old dream of becoming an astronaut, and as it's
nearly time for me to graduate from college, I need to start making
some decisions about where to go in life. Admittedly, I think that
any plans I make for this will probably go just about as well as my
plans to get into MIT or Rose-Hulman did (read: they don't get past
the application), but it's something that I'd like to have a little
more information on nonetheless. Any insights into this process that
you are able to provide are appreciated.

Thanks!

Daniel Huizenga