Quick Answer
The best way to study for AAMC PREview is to practice rating responses, then review why each rating is more or less effective. Start slowly. For each scenario, identify the main problem, the people affected, the student's role, and the likely consequence of each response. Then choose among Very Ineffective, Ineffective, Effective, and Very Effective.
Your goal is calibration. AAMC PREview scoring is based on alignment with a consensus key developed with medical education subject matter experts. Full credit comes from matching the consensus rating, partial credit can come from being one step away on the same side of the scale, and crossing from effective to ineffective loses the most ground. That means your first priority is learning the effective-versus-ineffective boundary before worrying about fine distinctions.