Your goals for the opening sentences of your paragraphs are similar to your goals for writing an introduction to a document. In the beginning of a paragraph, clarify the purpose. Most paragraphs in academic and technical discourse move deductively--that is, the first or second sentence presents the topic or theme of the paragraph and the subsequent sentences illustrate and explicate this theme.

Notice, in particular, how Chris Goodrich cues readers to the purpose of his paragraph (and article) in the first sentence of his essay "Crossover Dreams":

Norman Cantor, New York University history professor and author, most recently, of Inventing the Middle Ages, created a stir this spring when he wrote a letter to the newsletter of the American Historical Association declaring that "no historian who can write English prose should publish more than two books with a university press--one for tenure, and one for full professor After that (or preferably long before) work only in the trade market." Cantor urged his fellow scholars to seek literary agents to represent any work with crossover potential. And he didn't stop there: As if to be sure of offending the entire academic community, Cantor added, "If you are already a full professor, your agent should be much more important to you than the department chair or the dean."