It's tough to recommend general techniques for something like this other than "don't be a jerk." I'll share a couple of ideas that I've formed after years of mailing list interaction.

1) Be strategic. Sometimes it's not worth pursuing an argument if that will alienate people who are valuable to the project. You have to pick your battles. Often this means letting other people get the last word. If you've said your point, let them say theirs. You don't have to nitpick every single thing they say to you.

2) Let people save face. If you argue with people in a way that gets their back up, you will never win the argument. You have to give them a way to agree with you without totally humiliating themselves. That may mean checking over your own mails before sending to make sure you didn't say something obnoxious out of anger. Your mail will probably be sent to many people and archived on Google forever, and a nasty tone will probably not help you win the argument. It will inspire the other person to resist your ideas more.

Also, sometimes you have to walk away. If a project is full of people who drive you crazy and reading the mailing list makes your blood boil, stop reading it. Find a different project to put your time into. Life's too short.