When you get a chance to ask questions during a job interview, use the opportunity wisely. You want to show that you've done your homework. You want to convince the interviewer that you're interested in the organization and the job. You also want to learn as much as you can, for two reasons. One is that you want to know if the job, if offered, is really what you want. The other is that you may be able to use the information you gain to your advantage in the hiring process.
A good way to get some of this information is to ask: "What skills, education and abilities do I need to succeed at this job?" The answer to this question should help you know what to emphasize in a thank-you letter and in any follow-up interview. You can emphasize your strengths. If you find that you're lacking in some qualification, you might address that lack directly and suggest a way you could overcome it.
Read on for a variation on this question that might yield even more information.