Searching on "John Smith" will not find files that mention "John Robert Smith" or "John Q. Smith" since John and Smith are not together. A better search would be to use "John Smith"~1 - now the search engine will return files where John precedes Smith by at most one word.
(Use a larger number for more middle names - "John Smith"~3 will find John Smith, John Q. Smith, John Quincy Adams Smith, and John William Henry Johnson Smith, for example)
Boolean searches Entering multiple words on the search line will return hits that contain any of the words: "John Smith" "Mary Jones" finds files containing John Smith or Mary Jones or both.
Using "John Smith" AND "Mary Jones" (note the capital AND) finds only files that contain both names.
"John Smith" NOT "Mary Jones" finds files with John Smith that do not have Mary Jones in them. A plus sign (+) before a term "John Smith" +"Mary Jones" +"doctor" requires that Mary Jones and doctor have to be in the file. Capitalization of names is not necessary.
County names require some special handling. Multiple word county names are usually spelled without a space in most cases: Example: for San Luis Obispo County, type in sanluisobispo On occasion, the file manager has abbreviated or misspelled the county name. When in doubt, go to the Archives and then choose the state and see how the county name is spelled in its directory, as this is what the search engine uses.
The advanced options allow for searches of a single state or county or a particular type of record.
Here are some examples:
Returns only 1850 census files with John Smith (in that order) in them