Study up on your program of interest -- its requirements, history and course offerings. You will need to be specific and engaging in the essay, so don't exhibit any ignorance about the particulars of the school. Ensure that your personal objectives really would be a good fit with the institution before you write an essay convincing anyone else of that fact. As thoroughly as you research the graduate school, research your own history and memory to prepare important points to mention in your paper.
No essay is complete without a thesis. This is the guiding statement that unites all ideas within your paper. Include a strong argument about yourself and your personal goals in the opening paragraph. Be concise, clear and memorable. Include something individual about your background or your aspirations, and tie it in with the objectives of the institution you seek to attend. Once this thesis is stated at the outset, the rest of your piece must support that claim with relevant stories and facts.
Admissions staffers tire of reading generic essays that are indistinguishable from one another. Place yourself ahead of the pack by showcasing your superior writing skills, telling a truly embarrassing story about something you learned from or announcing your unorthodox professional plans following graduation. Don't be shy about announcing the ways in which you will contribute to the reputation of the school once you become an alumnus. Make the reader perk up, laugh a bit and raise her eyebrows at your transparency and assertiveness.
Your first couple of drafts should be relatively uncensored and freely composed. You need time to develop your initial thoughts into gems. It helps to show your unfinished work to parents, teachers and friends for honest feedback before editing new drafts. Turn a long, rambling essay into a succinct and well-crafted piece of art by trimming the fat and clearing up murky points, in addition to editing for grammar, spelling and syntax. Don't mention random anecdotes that have nothing to do with your thesis; rather, ensure that the entire paper boasts an undeniable cohesiveness and sophistication.