Considering it is now two full years since the OP asked this question this reply is (probably) purely for archival purposes if someone (like me) happens to stumble upon this question and finds it useful.

Professor Emerton's detailed comment on Professor Tao's blog is incredibly useful as a roadmap found here:

http://terrytao.wordpress.com/career-advice/learn-and-relearn-your-field/

Also, Professor Ellenberg has a webpage for prospective students who wish to be advised by him. On it he has recommended books to read in pursuit of this path.

http://www.math.wisc.edu/~ellenber/gradstudents.html

Considering it is now two full years since the OP asked this question this reply is (probably) purely for archival purposes if someone (like me) happens to stumble upon this question and finds it useful.

Professor Emerton's detailed comment on Professor Tao's blog is incredibly useful as a roadmap found here.

Also, Professor Ellenberg has a webpage for prospective students who wish to be advised by him. On it he has recommended books to read in pursuit of this path.