Tips for good searching at Google:

specific to this site:

on many files, county is abbreviated as co
most files have the county name in them, making specific counties easier to find
transcribing handwritten materials is hard, don't ignore alternate spellings or misspellings

you can go to Google and click the ADVANCED link to really drill down on a target
if you are not good at using multiple search terms, scroll to the bottom of the search results page and
"Search within results", you can do this as many times as you want
capitalization and punctuation are not necessary, try without
(i.e. St. Francis, st francis)

use "quotation marks" to indicate a specific phrase
(i.e. "bradley county")

use the plus + or minus - sign to to indicate AND + or NOT -
(i.e. you get a lot of hits for dallas, texas, instead of dallas county, use +dallas -texas
if you want to find two surnames on one page, +armstrong +mahurin)

after you click Search, you will have the option to limit the search to different categories
(i.e. bibles, churches, cemeteries)

use a plus + sign and quotations to add the county name in which you want to search
(i.e. +armstrong +"benton county" OR "benton co")