Well, you start a new thread just the same way you started this one : )
For example, to start a new thread in Site Talk while you're reading this thread either click "Back to Site Talk" at the bottom left of the thread (or click 'Site Talk' above the thread in blue). You'll then find the "start a new discussion" under the Site Talk title. Click the text box and a larger box with a space for your title and the body of your post will appear. When you're finished, click post, and your thread is posted.
Posting a topic works the same in each of the Categories-regional boards are for questions about where to find chow in different cities/areas and each of the topical boards are used to discuss Cookware or Home Cooking etc.
If you feel you've posted to a category in error (put an LA query on the Manhattan Category for instance) then simply 'flag' the post and we'll make sure it gets moved to the correct Category.