I firmly believe that it is incumbent upon each and every one of us to do our part to improve library staff salaries by taking a cue from Oliver and asking for a bit more, please. You're in the best position to do this at the time a job offer is made. This requires keeping your wits about you. It's easy to get so excited by a job offer that you just say yes right away. I suggest you always take a couple of days to think it over. It's okay to ask how long you have to decide.
If you make up your mind to ask for more money in advance, it's a lot easier to follow through. And you should always ask for more. You're worth it. But be prepared to articulate why.
If you have more than one job offer, use that as leverage. Call attention to your past experience, and if you don't have any experience, point out your unique qualities and explain how you're utterly fabulous.
If there's no budging on salary, what else is negotiable? More vacation? Money for conferences? Moving expenses?
(here's a tip: Sometimes it's easier to steel yourself up for this sort of interaction if you know it's coming. If you're expecting a call about a job offer, I totally recommend screening your calls. That way, you can call back an hour or two later when you're prepared. It puts you in control of the situation a bit more and gives you time to get your game face on.)
Being savvy when it comes to negotiating salary is part and parcel of the skills you need to be a good librarian. If you can't advocate for yourself, how can you advocate for your organization? That said, being savvy doesn't mean being unreasonable. Know when to push for a little more, but also acknowledge when it's time to concede, compromise, or back off.