Do you have posting incentives on your forum? Where users can earn points or something else and use that to upgrade or use the points towards something? I honestly always thought this was a pretty cool idea. Something that would be worth trying out.
Yes I do, they can earn badges and discounts for shops. We offer gift cards monthly to our top 5 users for the month to encourage people to post more. Just $10 cards and the top poster and member gets $25 gift card.
I didn't offer posting incentives on my previous forum. Instead users could advertise for free and gain more traffic and hits to there YouTube channel for free. I suppose this was an incentive for them to post on my forum because they wanted more subscribers.