That's a great list.
What I learned the hard way is that some buyers will try to take advantage of sellers, after the order is placed. It is helpful to have a good conversation and talk all details of the job before sending your offer, to understand how serious they are and if it's going to be a pleasant order. And it's okay to reject clients when you're too busy or you don't like their attitude.
Some of the best clients I've worked with, do not hesitate to answer any question I ask, and are happy to provide with anything that is needed. While some other clients will get annoyed even when you ask basic questions about the job.