Leave out the parts the reader will skip. The most common writing deficiency is an overly casual approach to the use of words. Vigorous writing is concise. This requires not that the writer make all his sentences short, or that he avoid all detail and treat his subjects only in outline, but that every word tell. In addition to using accurate words you will usually want to use familiar, simple, unadorned words.
Simplicity increases readability.
Complexity, unorthodox usages, transitional adverbs, and abstract nouns diminish readability. Strive for lean writing, using simple words. Avoid jargon, pedantry, or foreign phrases designed to show off your erudition. Arrogance pervades the work of certain scholars and professors. The greatest discovery in history is useless if no one understands what it means.