Start with the Basics -- Writing
Most law schools don't have their applications ready until September or October. In fact, most law schools don't even have paper apps any more. You must complete them through the school's web page or the LSAC online application service. Even if you fill the app out early, you can't submit it until October 1 at many schools. As a result, applicants put off preparing, and then find themselves suddenly behind schedule. But this need not happen. You can begin working as early as the summer before your junior year.
Focus on Your Writing Skills
While you're thinking about what to say, pay some attention to how you'll say it. The easiest way to "waste" your opportunity to wow them with your essays is by having poor writing skills. Boy, am I sick of telling people about their poor grammar. Kids, your grammar sucks. Instead of spending hundreds of hours reading the chat boards, how about learning how to write like a pre-computer-generation literate person? You'll have to, to succeed in law school. Better to learn now than after you get a "C" in legal writing.
Ten years ago I started a "wall of shame" of the worst mistakes that came across my desk (sometimes in the words of my own clients, more often in the writing of someone who asked me to take a peek, then got angry when that peek revealed poor writing). That list was by now so long that I surrendered; I've removed it before it got as long as the Yellow Brick Road.
I'm telling all of you, work on your writing!
I personally prefer the Harbrace College Handbook, but there are dozens of other good grammar and usage texts. The local community college's English class is using QA Compact, which is presumably much trendier, what with the cute red Vespa motorcycle on the cover. And the real purists might go for the The Chicago Manual of Style, the guru of all serious writers. I've linked to a recent copy, but what really can have changed since the last edition? So don't be afraid to go for an older one. To get beyond the technical points to stylistic and effective content, try William Zinsser's On Writing Well
Once you've brushed up your basic writing skills, you can begin working on the essays themselves.
"Less than more likely than not"
Huh? What? That's an actual IRS standard. It defines when the tax lawyer must file a Schedule UTP — "Uncertain Tax Position." In lay terms, if a tax lawyer is going out on a limb, he [gender choice intentional] must file a form with the IRS that says, "I made this judgment that I think you won't like." In legalese, his opinion is less than more likely than not to be upheld if the IRS audits the return.
Why am I telling you this? To show you the importance of both grammar and logic to lawyering. If you can't find your way through that phrase, you're lacking skills that you're going to need on the far side of the bar exam, so you'd best start acquiring them.