On your first visit, just take one garment and get a simple alteration to try the process out. Get in writing what the tailor is planning to do and make sure it matches up with what he expects you to pay for. Once you've found a tailor you trust, set a monthly budget and plan to...
She mentioned removing some excess fabric width in the front armhole area, and this must have been a last minute alteration, because she apparently did not make alterations to the notches, etc. after doing this, which I am guessing caused some of the problems with the sleeves and armholes....