Advertising for your business can be a difficult process.  Google, Yahoo, and MSN all offer their own respective options for Search Engine based advertising.  Personally, I prefer using Adwords as it is the most comprehensive, popular, and even yahoo is starting to roll it out on their website. 

Pay-Per-Click advertising is pretty straight forward.  A company designates a certain area of the webpage for advertising.  From there, a company trying to advertise will setup campaigns with one of the big 3 search engines.  The Search Engine will then determine what ads are relevant based on the content of a website and show the closest relevant ads.  For every ad that is clicked,  the company must pay a predetermined amount. 

In Adwords, a company can setup the maximum budget for a day or for a month.  From there, Google’s system will actually determine the amount of times the ad will show and can even spread it out throughout the predetermined time.  This software is very robust and offers many different options.  The enduser can see which keywords have the best conversion percentage and even chose keywords to avoid. 

There are also other methods that include Nextag, Revsense, and others.