If you're using Broad, Broad Match Modifier, and/or Phrase Match (and you probably should be), you must use Negative Keywords. Negative keywords are words or phrases that prevent your ads from showing when a user is searching for those keywords or phrases. Negative Keywords stop your Ads from serving on irrelevant searches, thereby saving you money on clicks that won't convert. Your Search Terms report is a great resource for finding words to add as Negatives. You can also view potential Keywords to add as Negatives by researching new Keywords via the Keyword Planner. To get the search term report in AdWords Account Select details and then go to All Search Terms. This will improve your Return on investment and improve your Adwords performance.