tested in April, so I started as soon as first semester of junior year ended (early december), did the kaplan big book once-over and a few kaplan tests by the end of break (mid-January), reviewed the material throughout the semester for a few hours a week until mid-march (spring break), and from there went through 8 of the AAMC practice tests (one every few days) and reviewed topics from the questions that i missed from said practice tests until the day of the test. this seemed to work moderately well, although i wish i would have given myself a few more months to study.
based on what many posters have said, I would actually recommend taking a summer to do some hardcore review and then taking it in august after your sophomore year. trying to study for the mcats really puts a damper on your semester when you have to juggle classes as well. in any case, best of luck to you!