I don't recommend starting a forum solely for making money off of itself. You have to be interested and passionate about your forum and then when people see that enthusiasm behind it, they would be much more willing to join. There are a lot of ways to advertise the forum: 1)Google adsense/Yahoo ads 2)Text links 3)Sponsor ads 4)My space 5)Affiliate networks 6)Contests (example: the person with the most posts wins a prize, points, etc).
The best way to earn would be to increase the site's traffic, unless you do that, there won't be any profit.
The irony of trying to make money with adsense and other paid advertising is that if your site is interesting and engaging then there is a lower ad click-through rate. Once upon a time I was involved in a popular auction-related forum with 3,000+ members. We had two paid banners, top and bottom, but the real revenue came from the sale of information products.
I'd say try ads. Pop-up ads would be good, I think. Also, you can start selling things via your forum if people trust you enough. However, you should start by building a reputation via a website first. Since I'm in the foreign language niche (not an easy one, I know, but it's my passion to get people speaking new languages), I'm going to use the AJATT (All Japanese all the Time) website. Basically, Khatzumoto, the webmaster, became fluent in Japanese in only 18 months. He had never stepped foot in Japan and never took a class or bought bogus software like Rosetta Stone. He was so amazed by his discovery that after he moved to Japan, he started up his AJATT website and began blogging about how he did this. He introduced us to his psuedo-Japanese home method, his philosophy for learning how to read and write the language, etc. He developed a huge following as people discovered that they could learn any language using this method - heck, even I have adopted a lot of AJATT in my own language journeys! Unfortunately, his site is very hard to navigate. It's really all over the place, and people wanted a step-by-step, none of the motivational stuff guide to how he did this, thus his marketing career started. He released an ebook about how you go about learning the AJATT way, and although the method has tweaked a bit since he started (AJATT is a learning process for him as well), the book is still downloaded quite a bit. Then came his sentence packs for download, then AJATT+, which required a subscription fee; and finally a forum. He's living entirely off of translating and AJATT+ right now, so it worked. It took years, but he really built this site up and helped a lot of people. What it all boils down to is that his followers trust him. He often times doesn't come off as marketing to you (marketing really seems like only a side thing to him), and seems genuinely interested in sharing with people how to get fluent in a language, kind of like LanguagePod101.
Actually you can decent revenue from forums but there is a big but - your forum should be very active.
You need to get a strong user base first. They only you can use that loyal user base for your needs. Get original and fresh content firstly.
If the heart of the forum is it's content then the blood is the moderator team. If you don't have moderators cleaning the forum and as well as contributing with content your forum will soon meet the fate of forums that are lost in the history.
earn the money in the Fourm.maybe the list some AD in the Forums .promotion your site or other way i have not thought ,
Well, for that you need loads of traffic, and by traffic i mean loyal traffic. You will require some really nice and original content for that. All the best
You could use other services to moneotise it i.e. offering template design or hosting on an admin forum.
Having a forum has huge potential. Here's why when you build a platform now your looked at as an authority. When you have folks coming to your platform now you control the ball game. You can introduce ads, subscription services, and many more tricks. Your also building a list, and what most forums don't do is capitalize on that list creating a high value email campaign, where you can sale to even more. Folks that tell you not to do it are just scared to make that big commitment. It takes alot of work to be an authority, but only 1% of the world takes that challenge. Your first step wold be to not listen to folks telling you that you can't make money off of a forum. The internet is only 16 years old, we are just getting started. Start your forum NOW, and just push the hell out of it. If you have the passion to make something happen you will make money out of it. Good luck and hit me up if you ever need some support.
as stated many times above, the best thing you can do is have many, posting members with ads on your site!