Be respectful. Don't read a few posts and ASSUME that it's your duty to set everyone straight. Lurk for a little bit to get the feel of the land.
Separate Questions from Discussions. If you have a technical question that you are seeking an answer to, go to the Technical Question and Answer section. Discussions are a gathering of ideas, and people will respond to your post with their own opinions. Short of profanity, there is very little babysitting in this section.
The Water Cooler is reserved for posting discussions that aren't related to business technology.
Thread-jacking is when you hijack someone else's thread. Remember that most people want to read what TechRepublic members have to say to the original question posted and don't have time to wade through the off-topic comments.
One thing that can help prevent this is the Votes button. Voting comments down will eventually cause them to collapse. The default is set at 5 votes down, but you can change this for your profile in the Community Preferences:
Please vote up comments and/or opinions that are helpful or that you appreciate.
Under the title of the Discussion, you can't miss the text that says, "Join the conversation!" Below that, you can click the RSS image to subscribe to the RSS feed or the envelope image to sign up for email alerts.