Be respectful, understand that it might be hard to hear your feedback and try and word it in the most direct way possible.
I think i might be missing another thing, but I forget. Those three things will get you far though.
Not sure that I agree with them being in a position 'above' you though. You are both adults. They might have more responsibility than you, but that does not mean that they are 'above' you. I treat every single person in the company I work for as an equal, from the junior consultants to the MD and chairman of the board. I also expect them to treat me the same.
You missed one very crucial bit of advice: Don't do in public. The split second your boss feels humiliated or under threat it is only a matter time. This also gives you an added bonus, your boss will trust you and believe you have his/her back. You have "confided" rather than exposed. Their egos love that BS. In many or even most cases, they will owe you one.
I mean, I'm not a very good boss; I think of most of my relationships the way you think of contractors. which is wrong for most people, but personally? I get really uncomfortable with this idea that I'm "above" an employee.
On the other hand, I think this actively contributes to me being a bad boss. A whole lot of people really like the idea that the company is a family or something, rather than it just being a mutually benficial relationship. I mean, if you are part of the company, and I own the company.... that has some (i think) disturbing implications. If it's just a mutually benifical relationship, on the other hand? that seems much less disturbing to me. But many people are more comfortable with the former. (and yes, many of those people like to see the company as more of a co-op where everyone has ownership, and that's another area where I'm a bad boss. I'm not any better at pretending that other people own what is mine than I am at pretending to own other people. I have enough experience with real co-ops and communes to want to avoid that sort of thing.)