Keep sentences shorter and sweeter. A blank line doesn't add much to the article length, so don't be stingy if it will help make your meaning clearer. Pick your words carefully. Writing with precision is as important here as it is in any other kind of discourse. Consider carefully whether what you have written can be misinterpreted, and whether that is something you wish to have happen.
People can only grasp about seven things at once.
This means ideas in a paragraph, major sections, etc. Avoid abbreviations and acronyms, if possible, and define the ones you use. There are several variations on any one sentence. A passive, questioning or negative sentence takes longer to read. Remember, most people who will read your posting do not know you.