HI Heather,
NAVTA has not yet developed a study guide for the AVA examination. When I've reached out to them they recommended that you know your eBook Textbook - "Textbook for Veterinary Assistants" very well. You should also be sure you go back and review your Penn Foster Study Units. Those study units were written to help guide you through the textbook, and give you the additional information needed that might not have been covered in detail in the textbook. Do the self checks, make flash cards for terms/topics, make sure you know the learning objectives (each textbook chapter should have a list, the study units have a list as well in the beginning). If you use those learning objectives as a study guide that should help you prepare.
Also note - there are some companies out there selling different AVA "prep" tools or practice examinations...DO NOT PURCHASE THEM! Most of these companies have re-purposed Veterinary Technician Examination questions, and so will NOT give you an accurate idea of the AVA examination. NAVTA has put out an announcement that they do NOT recommend any of those courses/programs at this time.
Good Luck on your AVA Examination!
Dr. Amanda