Writing essays is a painful but necessary portion of the grad school application process.  It’s not fun, but the essays are your best friend for addressing blemishes in your application and crafting your story (brand) for the school that you are applying to; this is particularly true for schools that selectively interview applicants (pretty much all of them).  Needless to say, it is worth putting in the required time and effort to write the best essays that you can.

After you are done writing an essay, you should definitely have someone (or more than 1 person) read through it and critique it.  Your first draft will never be the best version that you can write; this is very much an iterative process.   

Now here comes the tip, which I thought worked well for me.
<blockquote>Remove the essay question/topic in the copy that you send to the reviewer.  Ask them to write up what they think the questions are that you are addressing after they have read through it. </blockquote>If they miss one of the questions or the overall topic, and you are confident that they did a good job reviewing it, then that is a good sign that your essay is not written as clearly or to the point as it should be. At this point, do not be afraid to scrap it and start over if need be, though it is more likely that you can just make modifications to the current copy. 

I reviewed some essays from applicants for the 2012 class, and there were a few times that one or more required questions were not addressed at all.