Follow this checklist

Elements of a Comparison/Contrast Essay
Are there significant points of comparison or contrast between the two subjects you have selected?
Do you make clear comparisons or contrasts between the two subjects within the body paragraphs of the essay?
Are the body paragraphs organized either by point or by subject?
Have you used transitional words or phrases to indicate points being compared or contrasted?
Does the essay have a clear and consistent focus of comparing and contrasting two subjects?
Thesis Statement
Have you included a clear, focused, and detailed thesis statement?
Does your thesis state the subjects to be compared or contrasted and include the two or three points of comparison or contrast?
Is your thesis a single sentence located in the introductory paragraph?
Organization
Is there an introductory paragraph that contains your thesis statement?
Are there four or six total body paragraphs, each with a clear topic sentence?
Is there a conclusion paragraph with a concluding statement?
Have you used transitions to connect ideas between sentences and paragraphs?
Style and Tone
Is the tone of the essay objective and informative?
Have you carefully considered your word choices?
Is the purpose of your essay clearly to inform the reader about the similarities or differences between the two subjects?
Conventions
Have you checked your essay for grammatical and mechanical errors?
Have you used spell check or another method to check spelling?