Ask questions and get answers from experienced industry professionals
There are many types of custom builders out there, just like there are many types of homeowners. The one qulaity that is the most important is if the builders you talk to take the time to listen and to find out if you are a match for each other.
There are many one-size-fits-all builder types, but that is only acceptable if your goal is to create a one-size-fits-all type of space.
Take your time. Get a feel for how your builder answers your questions, and take notice how many questions he or she asks. At the end of the interview were you excited about your project? Did your builder present ideas and offer options that are budget appropriate? Do you know exactly where you stand, with a clear path forward? Do you feel comfprtable?
These are the most important questions. Truly, if you have found a builder who meets these needs, there are very few complications that can lead to a negative experience, because if you have someone you feel free to communicate with, then you have someone who you can work with.
Communication is one of the big differences between custom builders. Lack of communication on simple items or steps can detrail a relationship and cause many headaches.