This question is always a tricky one and a dangerous game to play in an interview. It is a common mistake to discuss salary before you have sold yourself and like in any negotiation, knowledge is power. Do your homework and make sure you have an idea of what this job is offering. You can try asking them about the salary range. If you want to avoid the question altogether, you could say that at the moment, you are looking to advance in your career and money isn't your main motivator. If you do have a specific figure in mind and you are confident you can get it, then it may be worth going for.