If there is a stem on either side of a note, or the stems are DOWN below ledger lines, where does the dot indicating staccato go?
On single-stem pitches, the rule is always the same: the staccato goes on the side of the notehead that is opposite the stem.
But when multiple voices are in play, the convention is typically to put the staccato pitch at the end of the stem, even if there's enough space to place it by the notehead. This means that, in multiple voices, the up-stem pitch will have a staccato above the pitch and the down-step pitch will have it below the pitch.
Note that in the first measure the staccato is centered with the notehead, but in the second measure the staccato is centered with the note stem.
The convention in these cases is to put the staccato dot above/below the stem of the note in question. I admit that it looks a little strange to have the dot so far away from the notehead, but that's how I've seen it done.