PPC research tools can be useful in mining keywords even if the mining is going to be for organic rankings. PPC tools may show the number of times a keyword is searched per month and also show the cost per click for each keyword. These tools also may suggest words that are similar to the main word that was search. If you can get a relevant similar word out of the tool you have mined a keyword. Search engines can also be useful in mining keywords. For example, when a search term is entered, a search engine will often give suggestions of other similar keywords.