Hi Abhi,
Never get into this discussion until and unless you are in the last phase of interview process.
If they question you in the first level of interview process then just say that why don't we discuss about this at the last round of interview.
If the same question is raised on the last phase of interview then you can decide the expected CTC based on the company standards(Small, Mid level, ISO certified, MNC etc). If possible before attending the interview, do a check in the portals to find out what is that this company is paying to their employees. Also check like what is that it is been offered to an candidate like you with your experience and expertise in the market. With this info i hope you can set your expectations.
It would be great if you can persuade the interviewer to reveal the package that they have thought for this position. If thats ok to you then proceed or else give him a range like 20% - 30% hike. Now its your skills to get on this.
Good Luck to you.
- Babu