When I sit back and think about all of the mistakes that I have made as a webmaster over the years. It's always been a short term vision of what I wanted to do with the project. And not realizing that many of the website/forums out there have taken years to establish themselves.
Especially today! If you're making a forum today I think you should have at least a 3 year plan or not do it at all. And during that 3 years you need to give it your all. You just can't throw up a forum and think people are going to join. You have to give people a reason why they want to join.
And I would also like to add that I am not mr negative. But plan on your forum failing because 99% of new forums fail. So don't invest anymore money than you're willing to lose.
Just a example I know a guy that spent over $20k on his forum, custom skin, custom add-ons, and a ton of paid forum posting and advertising. And his forum still failed. So don't think if you throw enough money at it that it will take off.
And last but not least there is no rhyme or reason why a forum takes off, It just happens. If there was a tried and true method of getting a forum to take off everyone would have a successful forum.
So never give up and keep you eye on the prize and maybe, just maybe you will be the 1% that makes it!