Mountain View, Calif.--Google Inc. Wednesday announced the availability of AdWords Select, an updated version of the AdWords self-service advertising system with a number of new enhancements, including cost-per-click pricing. This pricing plan enables advertisers to pay only when their ads are clicked on by users. Google's Premium ads will continue to be priced on a cost-per-thousand-impressions basis. Additionally, AdWords Select ads are ordered on Google search results pages in a new way. Unlike cost-per-click services, the top advertisement position (located to the right of Google's search results) is not automatically granted to the advertiser willing to pay the highest price. AdWords Select ranking is determined by a combination of ad performance (click-thru rate) and how much an advertiser agrees to pay per click.