Blends in but also stands out
The best practices to increase CTR is not only blending alone but also standing out quite a bit.
Joel’s site makes this point crystal clear, http://www.askjoelcomm.com/. The leaderboard comes right upfront of the screen, yet Joel does a good job by implementing a prominent image directly under ‘Ads by Google’, which is very clever in that visitors are often distracted by larger visual element from its nearby smaller ones thereby neglecting the ‘Ads by Google’ text.