PPC (pay per click) advertising is a staple of many e commerce businesses.  I don’t know of any site that sells a product online that doesn’t use PPC, at least every now and then. 
It can be remarkably cheap or bankruptingly expensive, unless you heavily target your keyword phrases.  The broader keywords are obnoxiously high, [...]

When using search marketing to promote your site or your product, you must decide what keywords are worth buying and which ones are worth the most money.
Choosing Targeted KeywordsWhile you can use Overture’s Keyword Selector Tool to find out what people are generally searching on in your industry, and how many searches are done, per [...]