How to answer the question: "What are your salary expectations?" in a job interview?

It should be in between ...not that high so you loose the position and not that low so they find it a chance to pay you less than you deserve

If they haven't mentioned their salary package, just go round the bush.

you can simply answer: "I would like to be compensated fairly for my experiences and if this is the right job for me, am sure we can come to an agreement on salary". 

The answer depends upon so many situations and factors like background of the participants, mode of meeting, your current status, position applied for... and most importantly--- how you carry yourself!!

Though simple and straightforward, but a tricky one. This is simply because if you quote a salary figure that is too high, you will definitely be running out of the opportunity as the interviewer would prefer a candidate with a reasonable minimum salary expectation, and if a number too low, it undervalues your work and potential and keep you dissatisfied at the later stage of your employment.

As Moses Otieno Radol said below "I dont get to an interview with salary expectations but i would hope that the would be employe will offer me a competitive salary that befits my experience and qualifications.   

I prefer that the salary is sutable with my current salary and with the salary scale at the new work

Means that how much salary you want for this job.. for me if my salary is 10,000 SAR and i am applying for same position to another company its means i am moving without any reason so i can move on same package or 10,000 to 12,000 but if i applied for higher position so i must check market and then maybe i will tell my expectations for 15000 SAR

The expected salary in any work depends on the nature of the work and the effort made in return, but the minimum that I accept to doing  any work is not less than 2100

Thanks to invite.

If you are well aware about the company's envoronment and have proved your self as per the expectation than claim with respect to your role otherwise let them decide depending on your performance/output.

Thanks for invitation,

I will reply;

To match with the market average for my qualifications and practical experience.

salary should be Best in industry and performance best in company.

Tell interviewer in a way that you are not seeking job for salary only but range should be upto your profile or at least define a number which should not exceed your career profile.