As a CFPC, I can tell you that my exam hammered E/M coding HARD. Know your AMA CPT rules for what constitutes an E/M level (NOT the Medicare guidelines for "medical necessity is the overarching criteria", etc) and don't go to sleep on all the other codes in the E/M section that aren't OV (e.g., critical care, emergency, etc.). The 90000 series should also be on your exam, but I can't remember how much
Also know your minor procedures - mostly the 10000 series. YMMV, but I don't think you will see anything from 20000-79999. Can't remember if there was anything from the 80000 series (labs)
If your job is funding this and you have not been through formal training, I highly recommend the AAPC Study Guide for CFPC - get the bundle that includes the study guide, practice exams, and exam
Finally, you will get to bring a separate reference material - I recommend a medical dictionary. Saved me on at least 2 questions. For taking my CDEO exam, I had to show my proctors what I was allowed to bring, so even for the CFPC, I recommend you print out and bring the approved reference materials sheet for the exam to show the proctors. This will definitely save some hassle if you don't have experienced proctors who know that there are other tests besides the CPC