When putting together a keyword list for a PPC campaign you probably use your favorite keyword research tool(s) and then either manually or with the aid of additional software, break out keywords into tightly-focused ad groups. These steps are vitally important in order to drive targeted traffic to your offer as well as for keeping your cost per click as low as possible.
One aspect of keyword research that a lot of marketers overlook or give scant attention to is compiling a comprehensive list of negative keywords for their PPC campaigns. However, a good list of negative keywords will go a long way towards filtering out unwanted traffic and as a result, lower you overall PPC spend.