Have a think about what a comfortable salary means for you before you get to an interview, making sure you know what your lower limit is. Do your research - Glassdoor, etc will be useful unless your role is a very unusual one. Then add 10-15% at the very least, more if you can't get a match when researching for what to ask for, but be thorough when investigating. Negotiate. Walk away if they offer less.
If they want you they will return with a counteroffer. If not, you didn't want it in the first place because you have standards.
I've been through the other side of job interviews more than my share lately, and while I have a decent idea of what a candidate will ask for - the numbers vary depending on location and experience, and sometimes other, more intangible skills - the fact is that the successful ones are the expensive ones. Don't ever be afraid to ask for what you think you are worth.
