Yeah post in general don't really matter. But meaning full helpful posts that aren't spam in the help forums count. I had a good 30-40 posts in the help forums before I applied for Support team if that helps. I also had a good(alot) number of posts outside of the help forums, which showed that I'm active and dedicated to the forums. So in other words just post more in the help forums, and post as you normally would in other parts of the forums as well. Not much I can really say besides "post more in help forums". But it's true... post more in the help forums and when you feel ready,
pm Dizzy with your application/request to join.
Edit: Oh yah when I pmed Dizzy my "application". I wrote about 3-4 paragraphs explaining why I wanted to join and what I could do for the forums and support team if that helps. Might boost your chances to join when you send in your request. Just a suggestion...