Search the Family History Library catalog for locations of interest (counties, states, townships, cities, etc.) even if you are not able to actually visit onsite. There are a growing number of microfilms that are available online digitally–the catalog indicates this by the image icon.
I was surprised to learn that the church I was looking for in Ohio had it’s records online–I didn’t even need to visit the library to use them. This is made clear in the film notes by the camera icon.