Maybe check with your friend? In some parts of the USA, especially in the southern states, it's customary to use 'ma'am' to address a lady. Otherwise, if this isn't appropriate, you should call her Mrs .. followed by her surname e.g. Mrs Smith.

You would call him "Mr. ___", and then you can refer to him as "sir" after the initial use of his name, during a given conversation. So, "Hello, Mr. ___". Then, if he asks you questions, or tells you something, you would add "Sir" after any short phrase. For example, if he asks if you are in school, you can say, "Yes, sir" or "No, sir", or if he asks you a question that requires a long answer, you can say, "Well, sir..." and go one with whatever you're going to say. You only really have to call him "Mr. ___" when you're first introduced, when you're about to leave, or when you're trying to get his attention. Otherwise, you can say "sir" in response to questions, or during the conversation.