This is just general advice that comes from years of experience of preparing documents for all sorts of different reasons, so take it and apply it / ignore it however you like. And of course, any SPECIFIC school requirements should naturally override anything I say in this post.
Font: I'd stick to a sans-serif font (no little tails or embellishments like you see in Times New Roman). They're clean and I think more standard now when it comes to business communication. Arial or Calibri are pretty universal and often Defaulted. Size wise, keep it around 11 or 12. Headers can obviously be a bit bigger.
Margins: Stick with the defaults again... about 1 inch all around. The only time I'd muck with these is if I was try to take care of a widowed or orphaned part of the text (i.e. 1 (or maybe 2) lines of a paragraph stuck alone on a page or or being chopped off at the end. Typically the most sloppy looking case is when your last page is nothing but a line at the top (the ultimate widowed line).
Essay length will usually be specified. If not, I'd say aim for 3-4 page, 1.5 spaced if it's not specified. Single spaced isn't bad either. My style for paragraphs is to NOT indent and have paragraph breaks (like this post) as opposed to indenting with no breaks (like you'd find in a book). Doing both indenting and breaking looks sloppy IMO.
Content wise: again, it's usually specified, But if it's loosely defined, YOU HAVE A HUGE OPPORTUNITY. Go out on a freakin' limb and write something a little funky if you have the writing aptitude to do so. I don't mean be stupid or pointlessly weird, but DO NOT just pump out the dry bullsh*t that you think that they want to hear. Listing your accolades, interests, generic goals... that's all crap and that's all what your resume will communicate (hopefully). I'm a firm believer that if you inject a bit of personality and creativity into an essay it will be NOTICED and REMEMBERED and your chances of landing that interview are so so so much better than the dude who did 10 points better on the GMAT and had .1 better GPA but their essay was a bunch of dry carbon copy that the adcom has heard time and time again for the past 18 years they've done this.
When I did my essay I spoke about goals and stuff, but I also talked about my childhood, I talked about how my relationship was an important part of my life. I spoke about how I was more of a nerd than a cool kid in school. There were phrases like "Even at 22 years of age, if you put me in a room with Lego I'd make something just for fun." I ended it with "Wherever I end up, I plan to make a difference and to inspire those around me to make a difference as well. I am confident I will. The only question is if you'll join me along my way."
Basically, I got personal. Confidence, not cocky. I got the interview, I got accepted, best choice of my life.
So I hope this helps. Remember that specific instruction from a school for their essays will override any advice here. Breaking their rules won't look too good unless you do it in an awesome AND are able to explain why you did so.
P.S. In looking at my essay, I actually used Indent, No Break style. So I guess I'm a bit of a hypocrite. I've been called worse. Good luck!!
I'm a current Corporate Residency MBA student at Dalhousie University (Nova Scotia, Canada).
This account is to help spread the word about this unique program, as well as to help provide a student perspective for MBA applications and GMAT experiences.
Every week I publish a blog about life in the CRMBA by interviewing current students. Find us on Twitter and Facebook, or post any questions/comments/concerns in this thread here on gmatclub.com
Highlights of the program include:
Specifically designed by Corporations/Employers, No work experience necessary, 8-month paid corporate residency, Grades/GMAT score not the main focus for admittance