A good interview has a comfortable , relaxing atmosphere and good preparation by both sides. There needs to be good lighting and a seating arrangement that allows everyone to make eye contact. Sometimes to break tense moments it is good to have humor. Water bottles and snacks are a good idea.
Good interview questions are questions that should not have a yes or no answer. The questions should allow someone to expand on the answers they give. Follow up questions that relate to the answer are sometimes very helpful.