The best forums have alot of contests . I alway do the contests that requires a new sign up and a deposit for bigger money Prizes but also have something for everyone to take part in .You may give out 100.00 in prize money but it keeps them around and when you ad more programs it converts to alot of new signups .I have some bingo forums and I pay a few people who play bingo with me to post in my forums.It works better when people have a genuine interest in what you are promoting.
Many forum owners also allow you to post your contests on their boards,Just try to have different casinos than the forums you are posting to.