Preparing yourself before any job interview is paramount. Know what you want i.e how much you want to receive as salary. Some find it difficult to voice out the amount they want to receive as salary thinking the employer wouldn't take them. But the fact still remains, always say your value, if they are not ready to pay the amount you stated, it then call for negotiation.
Again, some people look out for more like the benefits attached, health insurance and so on which is not a bad idea. You need to think about yourself too, your well being in the work environment and the possibility that the organization will care for you.