Adsense on forums is often a frustrating experience for new adsense users. Looking for a way to monetize all that forum traffic many new adsensers wind up on a forum themselves complaining about the poor returns. The following advice is based on my experiences of running adsense on forums for 2 years. ( I only successfully figured out what to do after being on WebmasterWorld and experimentation )
1. Topic is important.
If your forum is focused on car loans or investing your going to get better payoffs per click than if its about music. This is simple to understand so it should need no more explanation.
If your forum is in a low CPC ( cost per click ) topic then try putting in a for sale section, jobs section, an a wanted section. These will help build some better paying traffic for you.
2. Ugly URLS have got to go.
ModRewrite is a must ( assuming your using apache ), you have to have easily crawlable urls to get fully indexed in the search engines. Most of your clicks are going to happen by people reffered to your site not by your normal users, so the search engine referrrals are what are going to pay for the forum. Also your targeting will improve if your urls are simpler.
3. Regular users don't click.
Regular users of your forum are their to talk to other people not click your advertisements. Once you accept this and move on you'll be better off. I tested this several times by the following:
- showing ads to all users
- showing ads to only users referred to the site
- showing ads to only users not logged in.
The results were that regardless of who I displayed the ad's to I always received the same number of clicks. With this in mind I chose to stop showing ads to logged in users all together.
4. Position the ads right.
Use the heatmap over in the google optimization tips page. It works.
5. Cloak your content. ( WARNING: This is considered risky by some )
Cloaking is presenting different data to different users based on what you know about them.
Most forum software uses large html templates and presents unrelated text to the topic of the thread to the requester. This screws up targeting of the advertisements sometimes since often times the extraneous information outweighs the thread. Cloaking allows you to make sure the content outweighs the html and other crud.
What I do is remove all unnecessary information ( signatures, profile links, etc ) and present only the bare minimum to the adsense ( and all bots for that matter ) bot. This increased the accuracy of my targeting. Do this at your own risk. My recommendation would be to make sure the page is useful if it was sent to a regular browser and do not stuff keywords... just present the same data you would normally, albeit with a lighter html presentation. As an added bonus you can use this for cell phones and other small screen devices.
6. Don't hold your breath.
While all the tips did help me I still don't make much from the forum sections of my sites. You would do better to add a content section if you don't already have one and work on articles.
Best of luck!