PPC Strategies and SEO Strategies are natural bedfellows. While often seen as competing they are far more complimentary than competitive when used are part of the same Strategy.

SEO takes longer to build than PPC which can be turned on and off at the typing of a credit card number, what surprises me is that a lot of people do not use this advantage of PPC as part of their SEO Strategy.

My primary use of ppc within an SEO strategy is to test conversion rates and do split testing on landing pages while building the external link profile of a site. Basically I just set aside a nominal amount to allow me to do proper conversion analysis and come up with the optimal landing pages while building the external links to a site.  This way once people starting hitting the site from natural search I know that we have reasonably well optimised pages and processes.  Ok its not strictly scientific but its a hell of a lot better than having to change landing pages that already rank for terms.

I suggest that anyone who's looking at doing SEO for the long term take the oppurtunity you have during the first couple of weeks before you start ranking properly to use PPC to get your conversion process nailed.   Using this strategy has stood me in good stead and while meaning I have to spend some money on PPC upfront it inevitably gets a greater ROI earlier in the business cycle than waiting until we rank for given terms to optimise the pages based on user interaction rather than assumptions. It also means that we can much more accurately predict conversion rates based on keywords which helps with the overall business strategic planning.