I often tell the story of taking on a new client who had been running PPC for quite some time. One of the first things I did was review their search query report for the past year and because neither they nor whoever had been managing the account had been reviewing this report the client had lost thousands of dollars in irrelevant clicks. By adding these low and no relevance keywords as negatives we were able to turn the account from a lost leader to a success almost overnight.

The Search Query (or Search Terms) Report shows you a list of the exact search terms that triggered one of your ads to show. In my opinion you should review this report at least once a month for smaller accounts and weekly for larger accounts. This can be a bit time consuming but it is well worth the effort in terms of reducing low and no quality clicks which reduces overall spend, increases CTR and should lead to lower CPA as you are no longer paying for a ton of non-converting traffic.