However, we should not ignore the tools available, especially the tool to target relevant sites to show your ads. This is done when you create a new campaign (choose placement-targeted instead of keyword-targeted). Don't just look at the sites with lots of visits, but look at where the ads would appear, and if you are obsessed with your site's Page Rank, check out the targeted site's Page Rank before deciding to include it.
Your ad must basically be relevant to the keyword being searched or the targeted site being viewed. Of course, if the visitor can see value in your ad and there's a clear call to action, he/she would click through it and when he/she finds that your site too is relevant and in line with what your ad is promoting, then your chances of closing a deal is high =)
Hope this helps =)
