For example I have a music website for DJ. Only way for my forum members to reply and start posting I do promotions like the people who makes the best remixes for music will have a chance to win a free rank color on your name. After a few weeks after the promotion people were impressed and people started posting. So I suggest doing something like this to bring your forum members alive. If you have questions, leave it here.

Well this is mostly recommended when you have atleast 50 members in your forum. IF they don't post just do a little contest to help speed it up and also send emails saying we need more members, most people will help if you give them a prize .