Google’s Adsense program is probably one of the more effective ways to monetize a forum. Essentially, you place the Google Adsense code on your forum in the template for where you wish to show the advertisements, Google then displays contextually relevant advertisements from their pool of Adwords advertisers. If your visitors click on them, then you get paid by Google.
There are many options in the Adsense control panel to change the size, color and type of adblock to display. You can also block Google from displaying certain advertisement if you do not want them (eg from your competitors).
On the forum software side, there are many options available as to where to display them:
- As a banner across the top
- In the header or footer
- As a banner down the site
- After the first or third or whatever post you wish
- Inside a post
You can also display more adsense blocks to unregistered visitors to encourage them to join and log in to see less advertisements (see: Converting the visitor into a member).
Some of the forum software programs (eg vBulletin) have integrated the placement of Adsense into the software to make it easier. However, I do not use it (there is nothing wrong with it) because I serve all advertisements up to my forums and web site via OpenX and this includes the Adsense. The OpenX code for a zone is placed on the website and the Adsense code is then placed in OpenX and linked to the zone or zones. I prefer this as I can link several advertisement to a zone; I can rotate them; and I can geotarget them.