The guidelines for a SOP vary by school, and you need to follow them closely. Not adhering to the guidelines could be a reason for your not being accepted into the school.
The Parts of the Letter
Why are you applying? Graduate schools want to know why students are interested in obtaining a graduate degree, and typically look for an in-depth answer, not because "I can't find a job so I might as well go to grad school." A carefully thought-out statement of purpose is essential.
What is your experience? If you have an undergraduate degree in a similar field, you may be interested in continuing this part of your education. Conversely, someone with an unrelated undergraduate degree may be interested in expanding his or her knowledge. Others have been in the workforce for some time and are now ready to pursue a graduate degree.
Why this school? This is also an important aspect of the letter. Conduct thorough research on your school of choice so you can give a substantial reason for that particular institution. Again, stating that you were not accepted elsewhere is not a good reason, even if this is true.
What will you do with your degree? Why should a school use their time and resources to educate you? What you will do with the degree is of interest to any school, because as a graduate, you are a representative of that institution. Further, a school needs to know that your goals and aspirations are in line with those of the school.
Allow Plenty of Time
Just as the college admissions letter is important for undergraduate work, so too is the statement of purpose letter important for graduate work. It is a key element of your admissions application.
Be prepared to spend a significant amount of time on the statement of purpose letter. As much as you are able, begin as far ahead as possible. A couple of months or more is ideal.
Once you have drafted and reworked your SOP, consider having someone else review it. Someone who is skilled in writing statement of purpose letters, or has a degree or experience in English or journalism is useful, as these people are trained in writing.
Keep your reader engaged by focusing on the questions asked rather than including extraneous information (which uses valuable space). Demonstrate to the admissions personnel your genuine interest in your field and their school, and provide examples of how you will use your degree. These simple steps will help you compose an effective statement of purpose letter and increase your acceptance rate.