The difference between the symbols of a mordent and a trill is just a tiny vertical bar. Sometimes it could be misread when the print is blurred or too small. Is there a general rule, from the context, when each is used, so one can guess it right? I was thinking, maybe if the next note is higher, then it's probably a mordent; if the next note is lower, then it's probably a trill? But does it have to do with the previous note, too?
e.g. I mistook the following to be a trill when it's a mordent. My other question: for this one (G minor), should the mordent be played as F E F or F Eb F?