``What'' versus ``How'' (no, not Sacramento street names)

Focus on what the system is supposed to do, not how it is going to do it.

Not only must you focus on ``what'' and not ``how'', you also need to keep the interviewee focused during the interview. You can ask the interviewee to simply treat the information system as a ``black box'' that ``magically knows how to do something''. What does an actor want the genie black box to do (in the context of being an information system, that is).

One question you can ask (yourself or the client) is ``does an actor care that/about X''. If the answer is ``yes'', X may be a use case. If the answer is ``no'', X is probably logic internal to the information system that should not be captured as a use case. For example, does student (the actor) cares about check grade? The answer is obviously yes. One the other hand, does the manager actor (Dilbert's pointy hair boss being an instance) care about retrieving data from an SQL server? The answer is ``no, the information system is a mysterious black box as far as the manager actor is concerned.''