You'll fill out a LOT of paperwork (hopefully in advance) about symptoms and current meds. The doc will talk to you about all that, give you a few things to do, mostly supplements, that help most people with ME/CFS. You may get some info about behavioral techniques that might help in terms of rest and push/crash cycle.
The doc will order tons of labs based on your history and their experience. Those labs will almost certainly include the infections common in people with ME/CFS, thyroid, kidney and liver function (if you haven't had them recently), and immune tests. Others will depend on your history. They'll take lots of blood, so go well hydrated and bring water or electrolyte drink with you.
Some people get exercise testing and some don't. If you're coming from far away and you want the testing, you might call and ask if you can schedule it while you're there.
You'll probably walk out with some info to read and some lab requests for you to have done at home. What you probably won't get is new meds at the first visit. When the labs are all in, which will be a week or two for most tests (if you do them promptly when you get home) the doc will call you. At that point you make get part of a treatment plan and the prescriptions mailed to you. So, you aren't likely to have any new treatments for at least a month.
The immune tests take 6-8 weeks, so you're not likely to get an immune treatment before that. They'll call you when the tests are back, but it's hard to wait.
If you've not seen an ME/CFS specialist before, you'll think you've died and gone to heaven.
The doctors actually listen to you, know what you're talking about, take you seriously, and have concern for your well-being. I almost didn't know how to act with a doc who actually understands the illness, lol.