1. Go to Records and click the appropriate record type (e.g. Constituent, Gifts, etc.)
  2. Click Open a [type of record] (e.g. Open a Constituent)
  3. Click the link that appears in red under the results list: 
The search query is not the default. Click here to reset.
  1. ​The Search using query at the top of the Open window will return to <Default>

Note: This is specific to each user's settings.