We will practice what rhetoricians call the plain style, which means that you ought to aim for the simplest, most direct, unadorned, and unaffected style possible. As a guide, you should think in in terms of short sentences, averaging twenty words or so. Your paragraphs should have a clear topic with every subsequent sentence growing naturally from your intentions regarding its development.
Style is to be thought of as an instrument to achieve clarity of expression.
Your vocabulary should be jargon-free and designed to inform, not to impress.