Statement of Purpose/Essay plays a major role in admissions. This is the only thing where you can express your
goals, achievements impressively to admission committee and faculty members of your area.
If more than one students have marginal score for a particular University then these are the only things that will decide admissions.
You should give enough time to check and re-check your subject matter.
How to do it?
Get Complete information of the major your are applying and details of that major in the
University (you are applying).
See the facilities number of courses provided in that major. Does it matches your interests?
If your interests doesn't match you will most probably be rejected.
Some students got rejection letter stating "Your Research Interest
doesn't matches with any of our faculty member so you have been rejected".
Direct experience with your field of study is the best kind to have in your essay.
A word of caution: Do not focus solely on your research topic unless this is the standard practice of your field of study and you must outline your thesis. By over relying on your research, you risk your essay sounding impersonal.
Even if you have no formal experience, you might still have field experience that counts
Note: Don't simply copy sample essays available on internet.
How to write Essay-Check the Following
Do the first sentences express all of my main points?
Does my conclusion draw naturally from the previous paragraphs?
Does any quality, or skill distinguish you from other applicants? Why should College offer you admission? Think about it.
Have I been specific? (Go on a generalities hunt. Turn the generalities into specifics.)
Could anyone else have written this essay?
Regarding the introduction, is it personal? Is it too general? Can the essay get along without it?
What about the essay makes it memorable?
Remember successful professionals are extremely good at convincing others to
invest resources in them.