Excellent piece and thanks for sharing. I think all the points can boil down to one word: RESPECT. Respect for yourselves and the ladies. As in any situation in life, you really should put yourself in their shoes.
One point I'd like to add: Be sensitive about what you say and don't ask stupid questions (some of the girls told me the stupid questions they have asked) They mostly do not choose what they do, and they're just trying to make a living.
Another point to add I'd like to add: DO NOT HAGGLE! If the price is right, fine. If too expensive, be polite and decline; don't try to talk down the price. (Would you try to haggle at a hair salon that lists all their prices? It's the same, fee-for-service basis) There is nothing worse you can do to the self-esteem of the ladies by talking down their prices.
At the end of the day, we need to remember they are REAL PEOPLE (I had dinner with a lady last night, and she is as nice a person as you can find.)