Seeing as arguing is largely pointless, one of the best things to do is to severely limit what you end up arguing about:
Never seek out things to disagree with. There are too many of them out there, and correcting the ills of the world just isn't your job.
If you come across something you disagree with while randomly browsing, let it pass without comment (see rule 1). If it's truly frustrating, write a reply, then delete it without sharing it with anyone else.
Even in the limited scope remaining, it is not your job to correct everything you find that you disagree with. Try to limit yourself to things where the subject is at least something that makes some practical difference to your life.
Do not argue about politics, religion, or matters of personal taste or comparative morality.
DO NOT argue with Lisp programmers, believers in the Semantic Web, or furries.
Saying something controversial in your own space (i.e. your weblog) is only arguing if you directly reference somebody you are disagreeing with (or it is clearly understood in subtext who you are disagreing with), and that person is likely to give a shit about what you said.
If someone disagrees with something you've said, you're already in an argument. See below.
Once you find yourself in an argument, your job is now to make your point clearly, and then leave. You are allowed two passes:
State your case
Clarify any misunderstandings