In a comparison-and-contrast paper, you record the similarities and the differences of people, places, events, and so on. Be sure you omit any statements of the obvious (e.g., Mercury and Mars are both planets that revolve around the sun) because they will undermine the effectiveness of your paper. Comparing and contrasting two people — or places or works — that have many similarities makes for an interesting or informative piece only if you look beyond what's readily apparent and describe or examine similarities and differences that your readers may not have been aware of or have thought about.

If an assignment calls only for comparison, make sure you don't contrast — or vice versa. On the other hand, if the assignment calls for both, be sure you do in fact include both and give each approximately the same amount of space.

When you're writing a comparison-and-contrast paper, these transition words and phrases of contrast can be useful: after all, alternatively, although, and yet, at the same time, but, conversely, despite, even so, even though, for all that, however, in contrast, in spite of, instead, nevertheless, nonetheless, nor, notwithstanding, on the contrary, on the other hand, otherwise, regardless, still, though, and yet.

Transition words and phrases of similarity include again, also, and, as well as, besides, by the same token, for example, furthermore, in a like manner, in a similar way, in the same way, like, likewise, moreover, once more, similarly, and so.