It takes you some time to decide what the forum's title's going to be and what the forum's going to be about (you have to make sure the idea of your forum is not the same as other forums, lets say, you're going to make an anime discussion forum, before making the forum you have to search for other anime forums, if there's already an active anime discussion forum out there, it's really useless to make a new one, unless you're planning to compete against them), and how you're going to set the style and forums / sections / category up...
I've never owned any forum, I just administrate some, if I would ever start my own, the first thing I would do is look for a good free host, install a good free forum software (e.g. MyBB, phpBB, and so on), make a customized forum style, and set up the categories... After everything's done, I would install some add-ons I think necessary, post at least one Topic in each Category, and start Advertising!
And whenever I feel the forums are way too active, and I need a little help to handle any moderating or forum-related situation, I would promote the member who posts quality messages and who've contributed more than anyone / who've contributed a lot to the forums. One thing I would never do is promote my friends / best friends just because they are my friend, because, it's unfair from others' point of view, and they will have to earn the position just like every other members. When I can afford to pay money for my forum, I would switch to a vBulletin and a paid host.