Not every keyword you can dream up for your products is a good keyword to use in Google AdWords. When determining what keywords to use, I find it crucial to also think about the type of matching that should be used as well.
For some general keywords broad match should be considered off limits. A better use for some keyword phrases would be only phrase match or exact match. The default for AdWords is broad match. When you wrap your keyword phrase with ” it is called phrase match. When you wrap your keywords with [ it is called exact match. Google reviews your match type in determining how to show your keywords.
If you are getting many impressions but your click through rate is low, then you may need to carefully review what broad match keywords you are using and either pause them or show them instead as phrase match or exact match terms. Remember when it comes to broad match, Google adds other words in your phrase, before, after, in between, and even uses synonyms. In some cases your broad match term could be showing ads on search phrases that are not even remotely pertinent to your services.
I am not saying broad match keywords are not usable in a well structured AdWords campaign, but that thought should be given to the words before a match type is selected.