The first few years I interviewed people for positions on the team I asked a bunch of questions. Most of them were the wrong questions.
I asked a lot of "What if..." questions. You know, "What would you do if a customer comes up to you with a complaint about...?"
Questions that are based on speculation will only get you answers the interviewee thinks you want to hear.
Those are of no value to you. About all they can tell you is whether that person has done any research on your company's policies and values. They rarely show how the interviewee will actually react when facing that situation.
The right questions to ask are questions about their previous actions. Our actions speak louder than our words about who we are and what we believe.
Use this phrase, "Tell me about a time when..."
Tell me about a time when you went above and beyond your job expectations to help a customer.
If they can't tell you a time, then they probably never did. What they tell you also gives you insight into what they think is above and beyond. It tells you how they perceive their role and whether they even believe they can do what is right versus what is policy. You might also learn that they are mavericks who do their own thing regardless of what policy might be.
Tell me about a time when you had to help a friend in need.
You learn a lot about loyalty, helpfulness and what friend means.
Tell me about a time when you had to stay later than you were scheduled. (getting the job done versus just putting in the hours)
Tell me about a time when you were short-staffed and everyone had to do extra. (how they view hard work and stressful situations)
Tell me about a time when you received the worst customer service while out shopping. (their view of what bad customer service looks like)
Tell me about a time when you received the best customer service while out shopping. (their view of what good customer service looks like)
Tell me about a time when you had to solve a problem and no one was there to help you. (their approach to problem solving)
Tell me about a time when someone at work did something especially nice for you. (how they relate to other workers)
Tell me about the worst thing you ever had to do on the job. (how they get along with co-workers and bosses)
Actions speak louder than words. Decide which actions you want your employees to take, then ask them to tell you how they've taken those actions before. This one little tip changed the quality of my new hires overnight.
PS Some of your interviewees will hem and haw at answering these kinds of questions. They were prepared to tell you what they thought you wanted to hear. Take that as a sign. Others will tell you things that will astound you. If they get on a good story, keep it going. The longer they tell a story, the more passion you'll see and the more it will reveal.