Brilliant guide!
I absolutely agree with your point that sufficient content knowledge alone is not enough to tutor effectively, and that's something a lot of so-called aspiring "tutors" fail to realise (many of whom are on this very site). It's always amusing to see tutors show off their fancy ATARs, study scores, prizes, scholarships, etc., yet they show no evidence at all of pedagogical knowledge (i.e., knowing how to tutor effectively), which is far more important.
The key difference between effective and ineffective tutors is that effective tutors know how to draw out the best in their client (client-centred) whereas ineffective ones merely lecture the client and expect them to "just get it" (tutor-centred). From what I've read, most tutors on this site are tutor-centred in that they emphasise their own achievements (i.e., they're egocentric) and believe that their content knowledge will somehow rub off onto the client. You'll find that these types of tutors prefer working with many different clients for very brief periods of time rather than a select few over a longer period of time (quantity over quality), which doesn't show a great deal of regard for the learning process.
I'll be considering tutoring services for my son when he enters VCE (he's only 5, so there's still a long way to go!), but I know right now that the main things I'll be looking for in a tutor are decent content knowledge (i.e., "do you know your subject?") and, more importantly, pedagogical know-how (i.e., "can you deliver the content effectively?"). If I looked at a tutoring advertisement and all I saw was a list of the tutor's academic achievements with a brief passing comment that they know "the best way" to tutor my son, I'd close the window right away. In fact, I've yet to find a single tutoring advertisement on this site that doesn't fall under this category.
At the end of the day, a person who scored an ATAR of 99.95 yet has an appalling pedagogical technique (if any) and awful communication skills is about as effective as somebody who has an ATAR of 60.00 and shows superior communication skills and a willingness to bring out the best in their client. Nobody cares how high your ATAR is, whether you achieved multiple study scores of 50, whether you received a VCE Premier's award, etc., etc. The most important thing you can do is to demonstrate that you can actually tutor, and possessing sufficient content knowledge is only one part of the equation!