My advice, always use niches and specialized forums to "own a word". E.g. users visiting your website stormy.whatsoever will have a windpark in mind. General forums do not really work, due to the lack of a "word".
I have created a specialized maths forum: http://www.mathelounge.de/
- I filled it with 100 - 200 maths questions 4 years ago, questions that I before answered by email. Google picked them up and students started to find me. Now I have 20-25k visitors per day and about 65k questions and 83k answers.
On the other hand, I started a Lithuanian *general* q&a forum: http://www.klaustukai.lt/
--- I paid for the writers, I made donation games (I paid 0,50 € per incoming question). I made games, rewards etc. It just did not work out. Even though I have about 5k answers of quality content. This is actually quite depressing :D
So, again. Be specialized and own a word!
Hope that helps,