(1) Know the "commercial" stuff. A lot of people go into commercial rides prepared to do maneuvers, but without enough understanding of what a commercial pilot can and cannot do with their certificate.
(2) Focus a lot on the "multi" part of the ride. Know Vmc backwards and forwards. Know why and how the prop on a multi will go one way if oil pressure is lost and why it works differently with a single. Know why Vmc goes down as weight increases, and the answer isn't the common wrong answer that it has anything to do with momentum. Finally, if you know why Vmca is lower than Vmcg, you'll have a pretty good understanding of the trivia.
As far as the examiner, I hate preparing a a student for a specific examiner, but it really doesn't hurt to talk to their past applicants. That "bad reputation" most likely begins with poorly prepared applicants. Talk to them and ask what they had trouble answering and where the emphasis items were and then be prepared for questions in those areas.
Lastly, don't take what you hear about "bad reputations" too seriously. I've dug into enough such situations to find that the story from the other side often makes you wonder if you're even hearing two stories about the same event.
