Don’t stray too far afield from your core subject or you’ll wind up with a forum that tends to go off topic too far. Of course, you can take those off-topic posts and spawn a new forum from that material. It’s all good in the long run.

You’ll have a few users who post for a while and bring in more traffic with their content then they’ll move on. Often the others who followed them there will stay.

Just make sure your own post content fits the site well and see what happens. Always mention your forum anytime you can without overdoing things. Business cards often open the door to further conversation.