If you have entered some criteria on a search screen and decide you want to start over, you do not need to close your current search and open a new one- you can just clear the search screen and remove any fields that you have filled in.
In the bottom left corner of the search screen, on the same bar where you can see the number of matches as well as access the map or your search results, there is a little yellow brush/broom:
Clicking this button will clear out all of the fields and bring you back to a blank search screen. You may now start entering new search criteria.
*** Note: if this is a search that has some default criteria automatically filled it, clicking Clear will empty those fields as well. ***