2. The best colors are blue for the link - surfers know that blue means click me. And darkish almost black and grey for the text and url. No borders. The same background as your page. Will it merge into your content? No, that's bogus. There are maybe 4 surfers in this galaxy who can't tell a Google ad when they see one. They are not going to believe it's part of the text. Wake up, OK?
3. Another format which is being reported to more or less work is the full wide banner type layout with text ads and images directly above the links. Try it and see if it works for you. Maybe it's a fad.
4. Keywords and related content are critical if you want targeted ads. If you want high paying clicks you need to target the costly keywords AND have content that supports the keywords.
5. You need traffic interested in the ads. Which means your traffic generation techniques have to be targeted not scattershot. You might hear that 1% or 1.5% clickthrough rate is OK and 3% is good. Nonsense. Really successful people get CTRs that are often well above 30%. Even with modest efforts you should be getting an average 6 to 15% CTR (per ad impression, not pages).
6. You have to track what you're doing and you have to test variations in ad layout, placement, color and related content to optimize your income. No one can tell you how to do it except the traffic coming to your site. If you don't test and track, you're flying blind.
7. You need to keep building new sites.
