Google AdWords

AdWords is the largest and most popular of all the pay per click search engines. In fact, it's in a class all its own, with an index reaching over 10 billion web pages and 100 different language versions.
Google AdWords offers you benefits you simply won't find on other PPC search engines. Even if your site appears in Google's organic search results, using Google AdWords increases your exposure by listing your site prominently in its search results and its related search networks. You can edit your ads and adjust your budget until you achieve the results you want. You can vary your ad format and text continually, choose text or image ads, and target your ads to specific geographic locations and languages.

There is no minimum spending requirement or time limit. You pay a one-off $5 fee to register your details and once you've put your AdWords campaign together, it can be up and running within minutes. There is a minimum bid of $0.01 (although in most cases you will have to pay a lot more than this).

Like all PPC search engines, your Google AdWords ads are ranked by the bid price you are willing to pay, but Google also takes into account the relevance of your ad and will give precedence to ads with higher click-through rates. Therefore you could be paying $0.01 more per click than the advertiser ranked above you, but he has a better clickthrough rate, giving him greater "value", according to Google.

But like most Google interfaces there is the hidden, no-one-will-ever-tell Google algorithm that affects your overall placement in the bidding line-up.

You can create as many ad campaigns as you like, break them down into specific keyword clusters and bid on as many key phrases as your budget will allow. It don't come much better than that, folks!

Google provides great tools to help advertisers, including Google Analytics which is integrated with AdWords to help you discover which keywords perform and which you should cut. There's a Website Optimizer (in beta) which enables you to test variations of marketing content on your landing pages to see which version results in increased conversions.

Google also provides excellent tutorials for the beginner, to walk them through the process of setting up an AdWords campaign. (from http://www.payperclicksearchengines.com/directory/top-10-ppc-search-engines/google-adwords-l252.html).