Buy Praxis books, later or new edition. You borrow books from friends, state library or download audio books.
Carefully look for the PPST Mathematics chapter. Read its contents specially the categories:
Conceptual knowledge
Procedural knowledge
Representations of Quantitative Information
Measurement and Informal Geometry
Formal Mathematical Reasoning
Familiarize the topics, lessons or contents in each category. You need to master the concepts. Always refer to the definition when you are in doubt of the your answers or some terms. When you answer practice test exercises, always find out what makes it correct and wrong. Master those skills before going to the next level.
Set a time and day for study time. Do not cheat when you answer some exercises. If you like to have group study then organize and invite some of your friends but strictly do your work.
Do not stick to one reviewer. Any basic mathematics books that has contents related to your test, you must try to check it out.