Go to the CNet Forums home page:
Click the forum in which you wish to start a new discussion. Click the Create New Discussion button at the top of the forum. Your discussion topic will appear at the top of that particular forum. Everytime a new reply is posted to your discussion, the entire discussion gets bumped to the top of the list for that particular forum.
You can see all of your forum posts and discussions by looking at your profile
More info from the CNet forum FAQ: