When the given part of the sentence is "У мене болять", is there anything that signals to me whether I should be selecting "вуха" or "вухо"?
I always seem to select the opposite to what is required, and can never remember from one time to the next whether there is a subtle clue I am overlooking.
«Боля́ть» is the plural verb form, so it should be used with the plural «ву́ха».
«Боли́ть» is the singular verb form, so it’s used with the singular form «ву́хо».
Ah, thanks! ... so я and а, and и and о. I knew I should have been looking a little more carefully!
I don't know the exact rules, but singular is used in case "ear" acts as an "adjective" (it's not really an adjective). Ear pain, toothache, eye pain etc.