How would one go about finding a "good" cave diving instructor if not somewhat informed about the "bad" cave diving instructors?
Look at the boards- listen to those who have a lot of dive experience and what their opinions are .... Check out the type, length, and credentials of the instructor.
Are they both NACD and NSS-CDS instructors in addition to GUE, NAUI, TDI, IANTD.... Do they cave dive regularly, have they made contributions of note in the cave diving world (agency boards, book authors, diving style notables)..... Do their peers speak well of them... Do they respond to questions and give you attention BEFORE class begins as you are vetting them....
And consider how they structure their course... It's length, requirements...and limitations.