Topic sentences make it easier for the reader to follow the structure of your paper. They signal the purpose of each paragraph and relate that purpose to the paper's overall argument, answering questions about the paper's thesis such as how, why, and whatkind. One way of turning exploratory "ideas" drafts into finished products is to add topic sentences that clearly show the structure of your paper. So think about the need for topic sentences as you redraft.

As Writing from A to Z (fourth edition, pages 495-496) explains, topic sentences are "usually . . . most effective when presented as first sentences." This need for first sentence presentation is especially acute when your paper analyzes text. If you start a paragraph with a summary of text, saving the topic sentence for late in the paragraph, the reader can easily miss your valuable analysis. Your references to the text are there because they illustrate or prove something. Don't leave the reader in doubt about what that "something" is.

One way to practice writing topic sentences is by reading. Go through an essay and mark the topic sentences. Ask yourself how these sentences differ from the other sentences in the paragraph. Notice how different the essay would be if you left the topic sentences out. The information might still be there, but it would be harder to locate. Don't be fooled: often topic sentences will be the first sentences of paragraphs but not always.

Writing from A to Z quotes two successive paragraphs from an essay by Brent Staples called "Just Walk on By: A Black Man Ponders His Power to Alter Public Space." Whereas the first paragraph has its topic sentence at the beginning, the second paragraph places the topic sentence at the end (the topic sentences are in italics).

Paragraph #1: The fearsomeness mistakenly attributed to me in public places often has a perilous flavor. The most frightening of these confusions occurred . . . [Notice how the topic sentence sets up the illustration].

Paragraph #2: Another time . . . [Paragraph #2 begins with a second illustration, saving the topic sentence for the end of the paragraph]. Such episodes are not uncommon. Black men trade tales like this all the time. [This topic sentence sums up.]

Because paragraph #2 begins with a second illustration similar to the first one, Staples can save the topic sentence in paragraph #2 for the end. If paragraph #2 had changed the direction established in paragraph #1, an opening topic sentence might have been necessary.