Since you're a long way from actually taking a review course yet, there's only one thing for you to do: Read....a lot.
Get a subscription to the New York Times, The New Yorker, or even the Economist. Make a list of great books (no Dean Koontz or Danielle Steele crap) and read them. Not only will this help improve your vocabulary and sense of writing style, but you'll also be well-rounded and knowledgeable of current events which will help with both the MCAT writing section (albeit useless) and interviewing. If you're more interested in reading about healthcare issues, pick up a copy of Acumen (usually carried at Barnes and Nobles...not borders for some reason). Although it's a "health business" journal, it's got great articles on the current state of healthcare and what's really going on. All of these can be pretty dense reading, but they're worth it.