How to generate traffic to a forum / directory.

Since traffic and adsense revenue are directly proportional to eachother, i.e. the more traffic = the more adsense revenue, how does one get traffic ?

I'm well aware of using signatures, posting on other people's forums, radio and traditional advertising, adwords, paying for traffic, paying to have someone blog about the website, post exchanges, etc .. (I'm seriously considering purchasing bumper stickers at this point.)

I suppose that I'm just making sure that I don't forget something in the grand scheme of things. Lately, I have been earning over $1 per click on adsense, however, getting the people to click on the ads is very difficult.. especially in the light of low traffic.

In general forums are really hard to monetize. This is because a community site has many return visitors that know where exactly your ads are, so they simply avoid them. Try to display random colors on your ads, this will increase your CTR for sure. Also check google's page for forum placements

Now to get traffic there are so many ways, so I guess it would be better to tell us which is the site in question, to get more valuable info.

I would assume that picture ads (even google picture) are doing better for forum since a forum is by default pictureless (only few avatars) and a picture is something that might draw attention to the visitor

I don't have a forum so don't take my advice for granted, just an assumption