Every doctor has their own ways and every patient is different, but in all likelyhood, you will have someone take your vital signs, and possibly your photo for your chart. Then the doctor will come in and talk to you about when your symptoms started, what you have tried in the past, what tests or surgeries you have had, and what you have found that either does or does not work for your pain.
Unless you were referred and he has had time to look over your records and test results, he probably wont prescribe for you on the first visit, he might, or he might call your primary doctor with recommendations, and then your primary will prescribe. I have no idea which meds he will use, but he will probably start with what has worked in the past and try and tirate you up, or if you are on a short acting med, he may put you on a long acting one.
He may want you to try other treatments, tests, or counciling, these are all things that almost all patients in pain management are offered, Even if something sounds goofy to you, I suggest you try it, you never know when something will help, and it will show the doctor you want to work with him.
Heres where most people run into trouble. If the first thing or things the pain doc suggests do not work for you, dont start looking for a new one, good pain docs know it is a trial and error situation and will adjust or change any modalitys until they find one that is right for you.
Just make sure you and he are on the same page about what you want to get out of pain management, then keep going back until you and he are able to find that magical combination that gives you back your quality of life.
Remember the goal is not to be pain free, the goal is pain management. pain free for most of us would require a level of sedation that would destroy our quality of life as surely as the pain does.
I'm sure others can add to this, maybe someone from your area has a better idea of the local 'climate' of pain control clinics. If you have been reading the board, I'm sure you know they can be very different.
PS~You will probably also need to read and sign a 'pain contract', these are all different, but most say that you will use a limited number of pharmacys, not ask for early fills, or refills on weekends or afterhours, that you will not accept narcotics from any other doctor for the same reasons, and that if your meds are for any reason lost, stolen, or accidently destroyed, they will not be replaced. HTH