Make certain you know if they have the records/location you need in the database.
I was reminded of this when attempting a search in Ancestry.com's California, Voter Registrations, 1900-1968. The man I was looking for was in Colusa County. No wonder I couldn't find him--when I browsed the records, Colusa County was a no show.
Of course, Ancestry.com will let me put Colusa County in the search box.
It never hurts to "browse" the data by location to make certain it is actually in there. Otherwise you may be wasting time.