At the risk of stating the obvious, I thought it would be helpful to discuss how one goes about selecting the right tailor for the job.
Think about what you really want but be open to advice. The best results always come from collaborative work. Always has, always will. The art of tailoring is no place for the myopic gaze of the auteur. It is very important to know what you want (or at least have an inkling) so that when you pitch your idea to the tailor he or she has something to work with.
Don't be afraid to 'shop around'. The process of finding the right tailor has so many variables. Great tailoring doesn't just come from the acquisition of body measures. Anyone (and I mean anyone) can take body measurements. If it were as simple as acquiring measurements it could be done by robots. The art of custom tailoring lies in the interpretation of measured data and, more importantly, the ability to bring to life what you want. In my opinion the best relationship with your tailor is ultimately collaborative. In the same way that one wouldn't hire an accountant that doesn't get your type of business, or go see a therapist you didn't have rapport with, you've got to find a tailor that gets you. Tailoring (or at least great tailoring) is personal, intimate and nuanced. Don't underestimate the need to connect.
Don't buy the label and don't be duped by a long history. Just because a company has been making suits since 1850 does not necessarily mean that it will be the right fit for you. A brand's story and heritage are important points to consider but try and can keep your wits about you to ensure that they are delivering what you want. Sometimes it is worthwhile to ask yourself 'what is it exactly that I am buying?'
Ask to try on garments. Almost nothing can be divined from merely talking about a suit or a jacket. Clothes are boring on the hanger and built to be worn. You have to try them on to discover how they make you feel. If something does not feel to your liking ask about it. Trying on garments is the ultimate test in finding the right tailor for you.