In general, you need to know what the present effect of the particular disability will be on the student's functioning as a student in your class. Specifics regarding psychiatric history, diagnosis, and medications are not as relevant as the specific barriers that they present as the student attempts to complete the requirements of the class. Most useful is information about:
One of the best sources of information is from the student him/herself; s/he is the best source of expertise about the impact of disability and its effect on individual functioning.