QUOTE(SueHM @ Jun 4 2010, 06:55 PM)

Look at the melody notes at the cadence, and pick a chord that has that melody note in. Sometimes you will have a choice of two chords that fit the note - in which case, pick a combination that fits one of the common cadential chord sequences as detailed above.
Incidentally, I haven't noticed an example in actual papers for ages where there are two possible answers, though the workbooks do contain such examples.
I tend not to focus on the 'cadence' element of the question with students, and just say to find the right chords to fit the melody (using exactly your method), knowing that the AB will have supplied a tune that will dictate the right cadences! It might sound like a small point, but "find the right chords to fit the tune..." sounds much less scary than "Select chords to provide appropriate cadences ...."