I wasn't asked many hard hitting questions. The biggest concern it seemed is that you are reliable. My supervisors seemed to value this more than actually "liking" the person they were hiring. At this job, one of the biggest headaches for management is scheduling.
If you have a friendly disposition and seem to enjoy working with people with disabilities, that's a plus. However, if you have never worked in this field, be honest about that and let them know you are willing to learn. It's also important to tell the interviewer if you have a second job or attend college or have to pick up your child at such a date and time so they will know if you fit their scheduling needs (they'll probably find a fit for you). If you neglect to do this you may run into problems if you are hired and then spring this on them.