Good questions are always about opportunities for development in the role - what training is available to you to help you to do it better. Check that you get an annual appraisal. If the interviewers feel that you are interested in staying (not short term as a stepping stone to something else) that shows potential commitment. Don't ask questions about how soon you can take annual leave! Reasons for leaving current job (depending on what's true) could be that you have been there a while and would like to build on experience from current job in a different field, or with a new employer where you would be able to expand your skills. Good luck - let us know how you get on!