We deserve to make a living, and we deserve a modicum of respect.
The client must know what he or she wants.
The client must be committed to obtaining a successful finished product. This involves honoring payment agreements as per terms of the agreement, written or verbal (I suggest written).
The client must provide true feedback throughout the process, which means that the client can't be wishy washy. "I don't like it" is not valid feedback.
The client must provide the information needed to write the script, and products, samples and locations needed for shooting in a timely fashion. If the client doesn't want to pay models or actors, he / she must provide them.
The client (who chose the producer) should protect the producer if and when others from the company are participating in reviews. Protection means standing up for the producer and defending the structure and creative that he or she approved.
There are five points here, and I will extrapolate with real life examples in future entries.