Deleting a field - how to make sure there isn't data in there?

Deleting a field - how to make sure there isn't data in there?

A while ago, I set up a number of Custom Fields.  Now I realize I want to delete some.  How to make sure there's no data in these fields?

These fields aren't used, so of course they aren't included in my Layouts. So I can't run a search  (Basic Search | Edit | Choose column | run search) because, not being in the Layouts, they don't show up. 

What to do?  How to make 100% sure that I am not deleting data? 
I suppose I could include them in the Layout, run the search, check, and then delete. 
Is that the recommended route, or is there something simpler?