Testing Keywords with PPC (Pay per click)

If you have your list of keywords, you are now ready to start testing them. The reason for testing your chosen words are to see if you get traffic; the right traffic, using these specific words. An example would be, if your product or article is about "remodeling homes," and you use the keyword "homes," you may get people looking for purchasing homes, foreclosed homes, homes for sale, and a variety of other audiences that you don't want. This will cost you money because they are clicking on your keyword, but they are not looking for your particular niche.

Why use PPC?

You can set up a PPC (Pay per click) campaign fairly quickly and start generating traffic. Usually within hours, you can determine if the keywords you have chosen are of interest to visitors. I would say give it a couple of days since the internet is ever changing and day or two can make all the difference in the world.
This will not only save you time, but money and it is important that you test your words BEFORE you incorporate them into your content. Many times people will write an article, create a PPC campaign, and wait for the money to roll in, thinking when the check their results the next morning they're going to be rich. What they usually find out is that they have spent/lost money because they did not test their keywords and the visitors clicking are not converting. Many times what you think might be a good word actually isn't.

Conversion

Your goal is to convert your visitors to buyers. PPC is all about conversion. There are different kinds of conversions.
A conversion could be if a visitor clicks a link or a conversion could be someone fills out a questionnaire.
For example, if you have an affiliate product for "weight loss pills," and the affiliate is offering a free sample if a two-page questionnaire is filled out about the visitor's eating habits; for every person that fills this out, you will be paid. Your goal is to create quality content that will make a visitor want to fill the questionnaire out.

One the other hand, if the visitor clicked on your page, read it a few lines and went on to something else; this has cost you money, with nothing in return.

It depends on what you are trying to market and what strategies you decide to use. You must remember that content is the most important factor. A site my look pretty or be filled with colorful pictures, but that won't keep a visitor on your page. Good quality content will keep them focused and more apt to make a purchase, fill out a questionnaire, or whatever your goal is.
Once you have determined your keywords are attracting traffic, you can use your website, articles, blogs, or whatever you choose to create your content. Remember to create content that catches the attention of your visitors/potential customers, provide informative content, and always give your visitor the assurance that they are getting a deal-value for their dollar. Everyone wants to believe that they are getting the most bang for their buck.

http://www.revenuesource.com/search-engine-optimization-marketing/16276-how-test-keywords-ppc.html

http://www.seomoz.org/blog/when-you-should-pause-your-ppc-campaign