Quick Answer
Many applicants can prepare for AAMC PREview in about 10 to 25 focused hours. That is usually enough time to learn the task, complete timed practice, review missed judgments, and build a repeatable approach to the four ratings: Very Ineffective, Ineffective, Effective, and Very Effective.
A lighter plan may work if you already understand professional judgment scenarios and your early practice is consistent. A longer plan makes sense if your ratings swing unpredictably, you struggle to separate “somewhat helpful” from “very effective,” or PREview is required by schools high on your list.
The goal is not to memorize perfect-sounding behavior. PREview asks you to rate how effective possible responses are in context. Strong prep teaches you to notice who is affected, what responsibility the student has, whether the response gathers information, and whether it respects boundaries while still addressing the problem.