Need Help With High Ranking Long Tail Keywords

I am relatively a noob here so please pardon me if I am posting this on the wrong forum and tell me where my question should go.

Now here is my problem:

I have a 5-year-old domain site which is found by a number of long tail keywords.

My site is on the first page of Google, Yahoo and Bing for most of these long tail keywords.

Now if I understand it right, my site should be getting lots of visitors in this situation. But that is not so. I get around 20 to 25 uniques every day and these are not converting much for the offers or ads on my site.

After joining this forum, I learned much about keyword research. So I tried to search these keyword phrases on Google External tool and find that there is a good number of searches for these keywords.

Here I would like to mention that when making this site, I didn't know much about SEO. I did what I could understand from reading up on the matter on the internet. At that time I wasn't knowing about the importance of long tail keywords at all. However, somehow my site is found by long tail keywords which I never optimized or knew about.

So I would like to have advice on what I should do to make most out of these high-ranking long tail keywords that find my site

Would be looking forward to your suggestions and advice.

Thanks in advance

Togdil