STATEMENT OF PURPOSE
This is a piece of writing which describes your brain. The scientist you are and the one you purpose to be. It is also known as an application essay, Object for Graduate Study or cover letter. It is required by grad schools which are institutions of further learning offering PhD and Master programs.
The first draft is often always wrong. Applicants often write opening paragraphs that are too obvious, extraneous and space-stealing. It ends up being boring instead of capturing the attention of the reader.
One should dig and be retrospective. List your reasons for interest in a certain field. Why you love the field and why it completes you. You should tell stories briefly. These stories help to tell the reader plenty about you.
The statement of purpose should portray you as passionately interested in the field, intelligent, well-prepared academically and personally, able to take on the challenges of grad school, able to have rapport with professors and fellow students as well as the ability to finish the graduate degree in a timely fashion.
The length may vary from one institution to another. It however ranges between 300-1000 words. These words should be carefully selected by the applicant to avoid writing a lot which means nothing.
In case of problematic academic background, address that as well to reassure the committee that you are willing to improve according to scores attained in recent exams.
You should abstain from bad-mouthing your current college/professors. This shows how unpatriotic you are. Saying something of substance about each professor in the institution you want to join shows you have done your homework.
Mentioning each by their name shows appreciation for their work. Get advice from several of your professors and keep working on your statement of purpose even after submission.