Don't read or listen carefully. Light upon a couple of key words and give an answer which speaks to the most common questions, not the one being asked. Blame all communication problems on the caller. You, after all, were hired for your superior people-handling skills and technical knowledge. Remember that the human beings are only to be found in tech support.
Clients are never human.
Don't tell the client where the FAQ can be found. If the client finds the FAQ and the question isn't in the FAQ, insist that it is. If the client can prove that the question isn't in the FAQ, insist that wasn't the question you were asked in the first place. Keep the amount of time you spend answering tech support questions to a minimum. Short, evasive answers are always better than long, accurate ones.