Google Adwords -> Keywords -> See search terms... -> All Go back a few months and export the data into excel. Sort by cost, filter out any keywords that con

Google Adwords -> Keywords -> See search terms... -> All Go back a few months and export the data into excel. Sort by cost, filter out any keywords that convert at a cost effective cost per conversion, and look for trends in words that cost a lot of money and don't convert. If the words aren't relevant, add them to negatives. If they are relevant, figure out if they need their own ad group and more effective ad copy/landing pages. Rinse, repeat.