The first, and most important one, is that if someone asks "Can I ask you a question?" the canonical answer is "Is it in French? Because I don't speak French."
Question: "How do I... ?"
Answer: "Integrate and divide by 5."
Question: "What should I do with [some object]?"
Answer: "Set it on fire, throw it in the Charles [River]."
Question: "Where is...?"
Answer: "I ate it," unless the object in question is actually consumable or a person, in which case the answer is "He/She/It evaporated."
Answer: "To spite you."
Question: "How come...?"
Answer: "Because God hates you."
(Note: these two answers are actually interchangeable in certain circumstances, but the rules governing the exchange are complicated and I won't go into them here.)
Question: "Who [did some action]?"
Answer: "It's all Bradley's fault." (Bradley being finagler. Don't worry if you have no idea who he is; it's still his fault. Our testers are currently evaluating whether this answer should be replaced with "It's all Perlick's fault." We will send out a recall notice if this canonical answer proves to be more effective.)
Answer: "Last Tuesday," unless last Tuesday is a plausibly the date in question, in which case the answer is "The late Proterozoic."
I may have left some out. Please speak up if you know of other canonical answers that I didn't mention!