Don't wait until the end to ask questions, ask them throughout the interview. When the interviewer asks, are you familiar with X, respond and then ask if that's something you'll be using on the job. If you're familiar with X, ask more about their implementation of X. By asking questions, it seems like you've got a lot of options and are looking for work that interests you, not just trying to qualify yourself to the interviewer.
It also makes them feel like they are already working with you because that's what a good employee does when a manager gives him work: he asks questions about it throughout the process. He doesn't wait until the end when the manager says, do you have any questions?