What is the ideal charging behavior for a new Retina MacBook Pro? I've called Apple Support a bunch of times, but I got conflicting answers.

To my knowledge, new technology makes it okay to keep the charger plugged in non-stop, but I want to make sure I am properly caring the computer.
If you mean you may have to remove the charger when the battery is at 100%, even though (I don't actually know whether it does) mbp disallowed current input, i'd remove it anyway. 
I hope I answered your question.