How to promote online forum?

Hi DP friends,
I am trying to build some action at my online forum for a while and it seems that I am failing.
The forum is part of social network, there are good number of active members, though activity is very low.
The other components of my social network seems to perform quite well, for example blogging platform.
Any idea, how to boost activity of my forum?
Cheers
Kal

See original post by kalseo