Well I'm about to kick start my forum but I'm worried about how many sections I should add. I don't want to go over the top and add as many as I can which I see many other admins doing. Should I be doing this or should I keep forums to a minimum to make it look active and add forums while we grow? I think if I added a lot of differant categories it would attract a lot more people.
I would try not to add too many at the start. You can always add some later and move threads around into the new ones. But, as a new site, it is important not to make the place look 'empty' which is will look if you have 50 forums with 2 threads each.
Start with the forums you believe will get posts every single day, so when users return all the forums will have the New Posts symbol. Post a thread asking for suggestions or votes on suggested forums, and add them once there's demand.
I try to keep all my new ones to like 3 sections. 1. Member section for help/suggestions, intros and whatever else 2. The on topic sections for my site with no more than 4-5 forums depending on the niche 3. Staff area, that isn't accessible to the rest of the people Works pretty good starting out and makes it nice and easy to expand as it goes on.
I think you should start small (only add sections that are needed) and add as wanted or on an as needed basis. Like BSMedia, three sections seem reasonable for a starting forum.