[hedgeyerbets]

1) Hull covers the theory and some basic applications. If you're in school, this is the book to get. It's a reference used by every trader at the firm I work for.
2) Sticking to reading books until you graduate is a better idea IMO.
3) Yahoo finance is fine. Get an online subscription to WSJ, IBD, and/or fin times if you want and spend some time reading up every morning.
4) Being a stock broker is kind of a crappy job. Get good grades, if you're not at a top school try to transfer to a better one, and read the stuff listed above. Internships are huge, so do all you can to perfect your resume and interview skills. Oh, and math or physics is likely a better major to get into the trading world depending on what school you go to.

I just went through the job search process last year so I'd be happy to answer any other questions you've got. Fire away.