Hey lothos,
Forums are alot of work, and take alot of dedicated at the start, for starting a new forum these are properly the best suggestions for starting off...
1) Don't add to many sections to the forums; you can always expand and add sections at a later time, but remember the more you have first up, the empty the forums look
2) Get some NP$ and advertise on there, that you want them to sign up and post two comments for $10NPS or something like that, so the forum get's started
3) Don't make the forum too dark, dark themes are hard on the eyes, something like a cream or the default looks great modified with your graphics.
4) Don't go to overboard on making money on the first couple of months with spamming the forum with ad's and pop ups, as you will want re-occuring users
5) Interact with the members in your niche, also advertise on places in your niche so people will be attracted to the forums, also start some threads yourself and always make users feel welcome
Good luck
