Follow the directions given by the graduate school; these will vary depending on the school and the department. Some graduate schools will state exactly what they want, even the font size; do not do anything different from what is required.
Tailor your personal statement to the audience that will read it. Usually the committee will be composed of professors who teach in the program to which you are applying. Use a tone of voice as if you were speaking directly to them.
Brainstorm as much as possible. Think about and write down your long- and short-term goals, your skills, background, academic accomplishments and professional accomplishments.
Use all the information obtained from brainstorming to demonstrate how you are a perfect fit for the graduate school.
Write your personal statement in an active voice to keep the reader interested. Use strong examples and personal details and avoid clichés.
Explain why you would like to go to that particular graduate school--what opportunities it can offer you and what you have to offer.
Be realistic about your goals and confident in your abilities but not arrogant and explain what you will do after your graduate from the school.
Edit your personal statement. Your personal statement should not have any grammatical or spelling errors. Have someone with an editorial background look over your statement.