Writing Essays

Think of your application essay(s) as a part of a larger whole (including the letters from your recommenders, and any other supporting documents such as a list of activities and awards, resume, or transcripts).
Consider your audience; write for an intelligent, non-specialist. Make sure the terminology will be understandable to someone outside your field. The tone should be neither too academic nor too personal. Aim for economy, enthusiasm, and directness; eloquence is welcome, but not at the expense of substance or honesty.
Make sure all information is accurate and that you will be prepared to discuss in some detail anything you mention.
Do not pad, but do not be falsely modest either.
Do not try to guess what the selection committee might be seeking; they want to know you, not a fabrication.
These documents are writing samples; all the rules of good writing (clarity, conviction, and correctness) apply. They are read as indications of clear and organized thinking and effective communication.
Plan to experiment and try completely different versions.
Show your work to a number of readers whose comments you respect. Consult especially your department advisor and ask your readers to tell you what questions your essays raise that you might not have considered.
Revise until you are happy that you have made these highly restrictive forms ineffective reflections of who you are and what you want to do.
Keep to word limits and all other guidelines.
Proofread.

Personal statements are short; identify a few points (3-4) that you want develop; let the other aspects of your application present other important information. Use your personal statement to say what others could not say.
Personal statements are read quickly and often in bulk; yours should be a pleasure to read: it should start fast, quickly taking the reader into the heart of your discussion.
Maintain focus; establish a consistent story line. Consider one or two anecdotes that can help you focus and give a human face to your discussion.
Use this discussion to present a compelling snapshot of who you are and what contributions you want to make, and to indicate what your priorities are and the kinds of intelligence and passion you bring to your work.
In this regard, you may also want to weave in some mention of any skills or resources that may particularly recommend you. (But again, beware of merely telling when you might be better able to use a moment from your experience to show a number of the qualities you want to convey.)

The personal statement is an exercise in self-reflection. Questions to consider:

What errors or regrets have taught you something important about yourself?
When does time disappear for you? What does this tell you about your passions, your values?
What ideas, books, courses, events have had a profound impact on you? How so?
To what extent do your current commitments reflect your most strongly held values?
When have you changed? Consider yourself before and after; what does this change mean?

Start a shoebox: a place to keep random notes for your personal statement; be ready to write at any time.

Review these items occasionally; let them tell you more about what you want your personal statement to say.

Start writing drafts, experiments; you will know when a paragraph begins to gel.

Key questions to consider: where, when, who, what, how, why? (.doc)
A description of your course of study or project; topic(s), research focus, degree goals, methodology, itinerary, (budget).
Why you have chosen this course of study (at this particular institution, in this particular country). Or why you want to undertake this project in this particular setting.
Evidence that your plans are consistent with your preparation, academic qualifications, and long-range goals.
Evidence of project feasibility: knowledge of programs, courses, and facilities; cooperation of host institutions and individuals (professors with whom you wish to study; have they sent or are they willing to send a confirmation of their support?).
Perhaps why you are choosing a new area of study, or what makes your project particularly timely

This statement combines elements of the academic proposal within the framework of a personal reflection.
It should not force an unrealistic unity; you are not a totally unified person.
It should balance both components together effectively.
The balance of these two aspects will vary according to what best represents you and your goals. (Rhodes recommends no more than 1-2 paragraphs to present the academic proposal.)