How can I see whether a particular keyword is triggering my ad or not?
If you want to know specifically and accurately which keywords of yours trigger ads and what your potential customers are actually searching for:
Go to Search Query Report, You can use it to find out which keywords trigger ads and how users behaved when they saw them. You can then use this information to refine your existing keyword lists.
To find the report, log into your AdWords account, and go to the keywords tab of any campaign or adgroup. Select any or all of the keywords you wish to get more information on and select the “Search Terms” button at the top of the page. Now you will be able to see how many times the search term was clicked and if any conversions resulted because of those clicks.