Do a lot of practice problems. There are plenty in the book "Cracking the Coding Interview"
Use the tools you'll be expected to use for an interview with one of the top 4 companies (i.e. internet text pad, pen and paper, whiteboard)
Do several problems every day and you'll be ready in a few months. Make it your 9-5 and you can be ready in a few weeks.
It's all about practice! Good luck!
Also, if you can get in touch with a recruiter at those companies, they'll give you tons of helpful tips (mostly just how to practice and what to practice)
It's all about practice! Good luck!
Also, if you can get in touch with a recruiter at those companies, they'll give you tons of helpful tips (mostly just how to practice and what to practice)