Standard format for places in the USA

I have downloaded my ATM tree into FTM2012 and now need to standardize place names. I see FTM uses a standard format of city, county, state and country (USA) but I cannot find a reference that explains how/where to manually enter only county locations. For example, ideally, Dallas, Dallas, Texas, USA is the correct entry. But if the location is Dallas county, which is the correct entry

Dallas, Texas, USA?
Dallas County, Texas, USA?
,Dallas, Texas, USA?
something else?

If "County" is added, then should "County" be added even when the city is available, as with

Dallas, Dallas County, Texas, USA.

It would seem like adding "County" might have some impact on searching.

Thanks...


EDIT: That begs the question of independent cities that are not within a county.

Can anyone point me to a reference that has this kind of basic "howto" info...thanks again.