Emphasize the positive reasons why you are targeting a job with their organization. Refer to specific aspects of the work, company culture and employer which correspond well with your interests and skills.
Frame your move as a path to advancing your career without disparaging your current job. One way to do that is to reference the aspects of the new job which appear to carry more responsibility. Even if the new job doesn't have a higher status, you could mention that you believe it would provide a springboard for future career advancement down the road (after you have spent appropriate time in the first job and mastered it). You might comment that you feel that the job you’re applying for seems more aligned with your long term career goals.
Integrate positive references about you current job in your response, so that it is clear that you are not fleeing a bad situation. You are just seeking to improve upon an already good situation. Of course, you should avoid any negative references to management or the number of hours worked.
Incorporate some positive reflections upon rewarding relationships with supervisors, co-workers and clients, whenever feasible.
Consider giving an external reason for leaving. You might refer to factors such as relocating to a more urban area or looking for a job that is closer to home. Be sure that it is clear that this is not the primary reason that you are applying for a job at the organization. The primary emphasis should always be placed on the fit of the job itself. Perhaps you can explain that you are looking to take your career in a different direction or use your skills in a new way, and this position offers opportunities your old company lacked.
If it is a well-known (public) fact that your current employer has a shrinking market share or other financial problems you might refer to this issue after making a strong case for why the new job is suitable. Be sure to avoid sharing any proprietary information or painting an overly negative picture of your current employer's situation. A vague reference to your employer's difficulties will usually be sufficient.
