Gain some distance and objectivity before rereading what you have written or having it read and reviewed by others.
Reread and/or respond to your readers. Make marginal notes and focus on the overall effect of the essay rather than individual spelling, grammar, and/or style errors.
Guidelines:
Re-examine purpose and audience. Do you do what you intended? Do your readers understand your intentions?
Pay attention to the advice your readers give, but don't necessarily make all the changes they suggest.
Consider your point of view.
Make sure you are using descriptive details where appropriate.
Do all your details and examples support you focus?
What is NOT present in your subject that you might need to mention?
What CHANGES occur in your subject?
Make comparisons if they help you or your reader understand the subject better.
Be sure to cue or signal your reader with transitions that help readers understand:
space
chronology
comparison/contrast
Revise sentences for clarity, emphasis, and variety.
After you revise, edit for correct spelling, grammar, and style.