I bought the Schaums books in Geometry, Trig, Calculus, and College Algebra, and went through lots of problems. This was a big help, but they still didn’t quite do problems in the Praxis format.

Then I found a guy selling sample Praxis II problems. This guy actually studied for the exam and took it. His problems seem like they were written by someone who understands techniques for the exam, such as using the graphical calculator. So his stuff was a big help. His site is www.praxisiimath.com

Get a test prep book (I got the one from ETS, but there are many different ones out there.)

Take the practice test (as a pre-test)

See which areas you need to work on.

Get your hands on textbooks for those areas.

Practice, Practice, Practice.

I would take the practice test again, after some serious studying, before the actual test to see where you are at, and refocus your energies.