I would ask parents questions that encompass the following: What are the child's academic goals? Are there any routines or responses that are necessary for medical or behavioral support? Is the child a flight risk? Any allergies? If the child becomes upset, what are the best ways to calm her/him? What are things the child likes, and does not like? Who should be called in the event of an emergency?
Some great questions to ask a parent of a child that has a disability are like do they have any allergies, do they communicate well with others, are they able to feed themselves. It really depends on how sever the disability is to what kind of questions should be asked. Some children might just have a mental while other may be physical.
How can you tell you've made them upset? How well can they work with other kids? What kind of help do they need? Do they like certain things to be a certain way? Here's a little tip: do some research on the type of disability and try to get to know them in a way where you're treating them like a person, like a friend. Not like a disabled person.