To prepare for the Physics GRE, focus on mastering core undergraduate topics, ensuring familiarity with all concepts encountered during undergraduate studies. Essential areas include classical mechanics, electromagnetism, thermodynamics, quantum mechanics, and statistical mechanics. Utilize undergraduate textbooks as primary study resources, as they provide comprehensive coverage of the necessary material. Additionally, ETS offers past tests and outlines detailing the percentage of questions from various fields, which can guide study efforts. Accessing these resources on the ETS website is recommended for effective preparation.