I think there should be some common knowledge of someone who wants to become a forum owner. Or one that is in the process of building a forum. Many will learn tips and tricks of the trade of being a forum owner. But here are some of my thoughts to this.
1. Do you have something that is unique or do you offer something different than others with the same forum topic.
A.) If it is similar to others, what will make you stand out - Pick out your best feature about your forum and work it to the public.
2. Make your users feel special. Yet keep it on a professional level. You do not always need catchy incentives to pull the public in (although it helps).
3. Users like the ability to create their own usernames, avatars and sigs (signatures), to upload images etc.
A.) Provide an area to chat or shout out. Sometimes users need a break and need a mild form of entertainment.
4. Hire Mods (moderators). Offer the mods an incentive etc. Offer it in forms of money, commission. Or offer them some form of monetary gain or reasonable offer.
5. Be active in your forum. This is a major factor in a successful forum. Check in at least once a day and make a few posts, articles, corrections etc.
6. Hire paid posters once in a blue moon to give it a boost, flare, or spice.
7. Provide a contest or giveaway for your users. It can be in any form you so choose.
A.) Link Exchanges
B.) Cash
C.) Free Domain Names
D.) Anything You Think Is Feasible
8.) Provide links on your forum that related or have some relevance to yours. And throw in an offbeat one for entertainment and fun.
9.) Do Post exchanges to see what?s out there and being said.
10. Know your business. Do not be an egomaniac. It turns people away. Remain professional as much as possible. If you do not know an answer find out and refer/point in the right direction to user where to go.