Now, whilst I would love to claim that status I really think that hypnotherapists vary hugely in their methods and how effective they are.
There is also the matter of the how he/she interacts with the individual client.
From one client to the next the same treatment can have a different outcome.
Find someone who you are happy to put your trust and time with and expect good things. Presence of mind and the ability to visualize a positive outcome should never be underestimated.