Getting hired by FB/Gogle/etc is roughly a 2 step process:

- get past resume screening to the phone screen

- do well in your interviews

The first part can be done in a bunch of ways, including having interesting projects on your resume or getting a referred by a current employee.

The second question is largely things that are covered by the book "Cracking the Coding Interview". People report that studying this book and related online resources for a month or so is enough to do well in the interview process.

I don't really know how they review resumes, but you should apply to some jobs to see if you can get a phone interview; if you do, then all you really need is to do well in your interviews.