- Give some incentives to your users. Contests, revenue sharing etc would work.
- Make sure you post regularly, answer others problems. Nobody likes an empty forum. You have to work on filling it up to some extent until you get enough post from users.
- Get your friends in. Helpful friends could give you a hand.
- Use social networking sites to get new visitors. A small part of that may join you.
- Post as much as you can in other forums of similar niche. Thats a very targeted audience and free of cost. Make sure you have your forum url on your signature.
- It takes time to get anything successful. Constant hard work will get you the success. So hang on there.