The topic sentence presents the main idea. The topic sentence is written in a way so that there's a smooth transition of ideas between what was stated in the previous paragraph and in the new paragraph. Present the paragraph's key argument clearly and substantiate it with quotations and sometimes, with data. Avoid ending a paragraph with a quotation. End the paragraph in your own words, in a way which leads into the following paragraph.
Sentences flow well and have a build effect.
That is, they present ideas that are constructed in a logical manner. All sentences relate to the main idea. By calling attention to the main ideas of each paragraph you can see the logic and progression of the draft essay. A paragraph is unified when all its sentences develop or expand upon the main idea. Remember to remove the underline and bold when producing your final draft.