1) Avoid using words such as 'retarded', 'moron', and 'fool' - they undermine any point you are making.
2) Everyone is entitled to a valid opinion - if you think it is "wrong", don't use that particular word; rather, explain with reasons why you have a different opinion.
3) Respect that everyone is an individual with feelings. Be careful how you step.
4) Don't use straw man arguments. Definition: A straw man is a component of an argument and is an informal fallacy based on misrepresentation of an opponent's position. To "attack a straw man" is to create the illusion of having refuted a proposition by substituting it with a superficially similar yet unequivalent proposition (the "straw man"), and refuting it, without ever having actually refuted the original position. Likewise, hyperbole should be avoided at all costs.
5) If you don't use reasons to back up your point of view, then other people are entitled to ignore your point. Statements like: 'You don't understand the publishing industry' add nothing to a debate.
6) Always read your post before you unleash it on the public. If necessary, rant and then delete.
7) Never ever say something from the anonymity of a keyboard that you would not say to a person's face.
8) Never SHOUT!
9) Try to understand the meaning of someone's post before directly attacking it. Have you read it correctly? Did you read what that person intended? If in doubt, ask.
10) Take any personal issues away from Internet debates. They do not add anything.