Explain your proposed course of study. Instead of a generalized view, be specific. By this time in your educational career, you should know the direction you want your studies to take.
List your reasons for wanting to pursue that line of study. Your application needs to stand out among thousands received by other hopeful students. The committee is looking for passion and purpose in choosing your major.
Detail any experience you've had to date in your chosen field of study. Former jobs, internships or volunteer work that relate to your major will boost your application. In your statement of purpose, let the officials know that you've already worked in the field and your experience has heightened your desire.
Read the school's brochure and talk to current students to get an idea of the type of student the school wants. Although their decision doesn't hinge upon your personality, it helps if you fit in with other students who attend.
Be honest but be forthcoming. The statement of purpose is your best opportunity to show the admissions board who you are. While your transcript and course choice plays a large roll, they want to get to know you as a person.
Check and double check your statement of purpose for grammar and typing errors. A hastily written letter with mistakes won't set a good impression. The admissions board is looking for a professional representation of your goals.