I don't think there is a fool-proof way to find a good hypnotist, unfortunately. I actually found mine in the phone book. This was when I lived in NYC. I found a great one, but had earlier gone to another one I didn't like at all. The good one focused on the message that "I am a non-smoker," not gory stuff. There are some who do group programs at hotels and such, too. Some good, some not so good.
It did work great for me -- and I really liked smoking. I still dream that I am a smoker!