Kevin Gibbons gives us six golden rule on choosing keywords to improve pay-per-click campaigns. For starters, consider specific and relevant keywords, rather than broad ones, he writes. The risk of not choosing relevant keywords could cost you tons of money because whatever traffic the words push to your site could leave quickly and never return.
All traffic isn't necessarily good. The keywords need to not only attract traffic to the site, but keep people there longer and coming back for more information, writes Gibbons. The post also links to rules that might come in handy when designing a paid search campaign, as well as measuring results.