How you say something is just as important as what you say. It is incredibly important that we convey an air of authority and dependability to the students. Always try to speak with professional confidence. Be polite but firm. If you cannot say something definitive and helpful, then either seek out a better answer yourself or pass along your question to someone who is better suited to answer the question.
Authority combined with ignorance is the worst of all.
Keep your responses as terse and unambiguous as possible. If you can't respond with an answer, respond with a promise to have an answer soon. In answering questions, no guessing. If you know the answer, say it directly. If you don't know, find out.