Twining Original Design's SEO Guarantee -
SEO Ranking Guarantees Have an Abominable History
Top organizations that promise SEO consulting and development seldom ever guarantee results and almost never use promises as a marketing tactic.
From the back in the Nineties through to today, SEO scams have used promises such as a guaranteed rank or a guaranteed amount of traffic as a lure to pull in prospective clients who underestimate the complexity of reaching truely high value SEO goals.
In the case where an SEO company tries to guarantee rankings it should be noted that typically the fine print will reveal that any guarantee is dependent upon the agency providing the service selecting the key-phrases. These key-phrases my be of little or no value to you.
The Search Engines Warning
From Google: "No one can guarantee a #1 ranking on Google. Beware of any companies that claim to guarantee an exact rank, or worst of all indicate some special relationship with Google, or that they have a former employee of Google who understands all of Googles algorithms.
The metric should always be traffic - increasing search traffic means the SEO is doing their job. Making the rankings of a few top phrases the priority above and beyond the overall search traffic means that goals are out of whack. Don't forget that 70% of search volume is in the tail of the demand curve - and there's usually a lot more low hanging fruit to be found therein.