...and don't let them sedate them to do a simple exam. If they can't do it without sedating, get a new vet!
Take some treats with you so they can have a goodie. I've never had a problem with any of mine giving a "fresh" stool sample at the vet...
If you have a female your vet should take a look at her pouch to make sure all is well and you should get a current weight.
They'll look at eyes, ears, listen to heart...some will try to look at the teeth...NO TRIMMING GLIDERS TEETH! If they mention it, RUN!
My vet, as she held Ariana felt her joints to make sure she was nice and flexible with no stiffness in her joints.
They should also discuss diet with you. Mine did and she even "quizzed" me on cage size and if Ari was a "lone" glider. When I said no, she was going to be put with my current 4 she proceeded to quiz me on intros. I could tell she was seeing if I knew what I was doing.
Not all vets go that indepth but if not, those are some things you can ask them to do, like..."hey, can you please check her joints for me, her teeth?" Anything you are concerned about....don't be afraid to ask.
You're paying this vet, they are providing you a service so you need to feel comfortable and not leave with more questions than you came with.