Statement of purpose (SOP) is an essay that you send along with your application. It describes your academic background and strengths and helps the admission committee to know what is important to you, and what your values and career goals are. To write a good SOP -

1) You just need to be honest and straightforward and dont exaggerate your achievements. Admission officers are well-trained and can easily spot a fake.

2) Be original with your essay. Dont copy it.

3) Check and recheck your essays and SOP and avoid obvious grammar and spelling mistakes.

4) Follow a logical flow in your essays.

5) Use words that you normally use.

Good Luck!!!