Kryzak's #2 rule (I'll do this piecewise, since I'm out of town this weekend): Give yourself a LOT of time. Start writing some "practice essays" early to answer the common questions of leadership, extracurriculars, innovation, challenges, uniqueness, and of course the Why MBA/Why Now/Why X School. If it's your first time applying, give yourself at least 1 month per school of essay time. You may not need it by the end, but you'll be glad to have it.
Start with a school that has a lot of essays that cover most of the questions, like Kellogg, Haas, and HBS. Once you can answer these and refine the essays a few times, go on to your least important school. Work on that, refine it until it's good, then move on to more important schools. Reiterate. By the time you get to your last school, you should have VERY polished essays. Now, GO BACK to the first school you worked on (Kellogg, Haas, or HBS) and you'll realize you can polish that up even more, even though when you first finished it, you thought it was gold (the "biryani" effect). This way, you don't sacrifice the quality of the schools you apply to first, and you still get the benefit of applying to your most important schools last. If you have time, go to your 2nd school (the least important one) and see if you can refine that again. Reiterate until you're sick of essays, then submit!
I'm not sure if others tried this method, but after I went through my R1 schools this way, I swear by it! (maybe I should call it "Kryzak's Method?"