Although I haven't started drafting my essays, I came across these tips on how to write a captivating personal essay on the Harvard Psychology Department's Graduate Program web page, which I thought I would share with you. I haven't read tips like these before, and they seem like they would make for some mature and well thought-out essays.
"In essence, essays that capture my attention are ones that develop ideas, propose experiments, point to holes in the literature, and do these things with passion and excitement. These very general comments, which will certainly not capture every advisor’s perspective, or even the majority, can be distilled to a few essential ingredients, presented below as questions:
• Why continue on with your education? Why do you need to learn more? What skills, theories, and knowledge do you lack?
• What are the kinds of discoveries and theories that sparked your interest in the chosen discipline?
• In graduate school, what kinds of questions do you hope to address? Why do you think that these questions are important? Given the set of questions that you will focus on, what kinds of methods do you hope to apply? What skills do you bring forward as you enter graduate school and which skills do you hope to acquire?
• What holes do you see in the current discipline [big picture stuff]? In what ways do you think that they can be addressed during your graduate career?
• What kind of graduate environment are you looking for? Are you particularly keen on working with one faculty advisor, and if so, why this particular person? If you are leaning more toward a cluster of advisors, as well as the department more generally, why? Hint: faculty are engaged by students who have read some of their work, have thought critically about it, and wish to develop some of the issues addressed. Further, it helps with admissions to have one or more faculty championing your case.
Essays that have the above ingredients are truly informative. They tell each faculty member why the candidate wants to go to graduate school, what problems they hope to tackle, what skills they bring, and which skills they hope to acquire. Following this format is, of course, not a ticket of admission, but it will certainly make your application more interesting and informative."
Taken from: http://www.isites.harvard.edu/icb/icb.do?keyword=k3007&pageid=icb.page19815&pageContentId=icb.pagecontent44114&view=view.do&viewParam_name=appinfo.html#a_icb_pagecontent44114