Good proofreading is always helpful. If nobody is available to proofread your work, you can do this yourself. After writing your material, put it aside for a day — at least several hours. (This breaks mental sets you might have that keep you from noticing problems.) Then read it aloud as if you were reading someone else's work. (Reading aloud slows down your reading, so you are less likely to skip over problems.)
If your reading goes smoothly, that is fine. However, wherever you "stumble" in your reading, other persons are likely to have a problem in reading your material. Those "stumbles" indicate areas that need revising.
Once you have made your revisions, repeat the process above. Good papers often require many drafts.
I searched Google under the key words "writing essays" to get these possible sources:
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
I hope this helps. Thanks for asking.