A specialist alcohol counsellor should be selling themselves on their skill and experience in alcohol or addiction work alone.
Many general counsellors will list 'alcohol problems' in their list of specialities, but often they say this because they believe they can treat underlying problems that lead to drinking. This is not the same thing.
Specialists will either have a relevant professional qualification (eg registration as a doctor, nurse, social worker or occupational therapist) coupled with experience in alcohol work, or they should be registered with the Federation of Drug & Alcohol Professionals .
As with choosing any other service, don't be afraid to check on their qualifications and experience, make sure you trust them and don't be persuaded into make a financial commitment early on.