Methods of determining values of keywords in an internet search are described. According to one aspect of the invention, a method comprises steps of receiving keywords entered for a plurality of searches; detecting converted transactions associated with the plurality of searches; analyzing the converted transactions; and determining values associated with the keywords based upon the converted transactions. According to other aspects of the invention, methods for recommending subsets of keywords and for recommending keywords based upon converted transactions and click through rates are disclosed. A database search system is also disclosed.