What you first need to do is establish what you need to maintain your lifestyle and how much that will cost you. From there you need to increase it to a reasonable point above what you would like and what you believe is reasonable possible given your education, experience and related employment attributes and offerings given the reasonableness of what can be expected salary-wise from the position you are seeking employment. This way you will have the knowledge of what you require and have given a figure as to what you don't really expect and a buffer-zone of where you may land in the range and the minimum you really need to live how you would like.
