My college and search guru Danny Sullivan once said something like this:
“Tap into the tail, and you’ve got sizable traffic, as well as traffic that often is reported to convert better than less general terms.”
There are number of companies that forget the long-tail of search both for SEM and PPC and by doing that they are missing out on great opportunities reaching possible clients, my experience is that the long tail search words often have much higher conversion, do cost less to buy through PPC and there for have much higher ROI (eROI).
Let’s say that you have a big site, tens of thousands of pages. If you optimise 100 pages for the same amount of phrases and all of them are ranking well you will still get the bulk of your search engine traffic through search terms that you have not optimised for, these would be the long tail search phrases.
By understanding what the long-tail of search stands for you can then use that knowledge to reduce PPC cost and increase eROI (ROI). While the phrase; Hotel in central London, returns traffic on hotels central, central London and Hotels London you can but a [ ] around it and then you have a exact match (Google), then there is advanced match (Yahoo) and so on.
By using a mixture of broad mach, exact match, phrase match and negative match you can maximise your conversion and the eROI on you PPC campaign. More here http://adwords.google.com/support/bin/answer.py?hl=en&answer=6100
And finally always use web Analytic tools like IndexTools to monitor your campaigns, I can’t recommend using Google to monitor Google and Yahoo, MSN or MIVA will never allow you to monitor their traffic through GA so to get the best picture use a third party solution like IndexTools or Webtrends.