Not all click-through traffic is equally good traffic. I enjoyed this article on DMNews about the different importance of clicks in the world of search. The authors point out we need to consider the keywords users have clicked before landing on our site (it's different if they search for "buy hi-fi, or they type "hi-fi review"), but also we need to analyse the path of "clickers" through the site, to see if they browse and leave, or they browse and buy.

Furthermore, before starting the campaign, it's also very important to evaluate the kind of search engines we want to advertise on. Users with different characteristics use different search engines. For example DMNews explains: "AOL traditionally has been seen as the search space of choice for the less Web-savvy Internet user. That might make it a better place to sell a beginner-level product that helps people understand the Web better.".

Planning has an important role also in search engine marketing. It's not just a question of choosing the right keywords, it's also relevant where you place them.