Keep asking until you know what they want.

The first rule of answering any reference or information question is to be very certain you know what the person is really looking for. Sometimes one has to ask several additional questions to arrive at the conclusion.

Tonight's example: a student asked where to find "chemistry books." I could have just sent him to the QD section to let him browse, but instead asked if he was looking for a specific book, such as the text book for his course. He let me know that all he wanted was the Periodic Table of the Elements... which I let him know was in the dictionary under "P." Since the dictionary was within sight of the desk, I walked over, opened it to the correct page and he set off to photocopy it happily.

See? I can be helpful when I want to.