When it comes to identifying credible information sources, I don’t know if there’s much more I can add to what’s already been said regarding the steps one can take. Determining the source’s authority/credentials, checking references and dates, verifying claims with multiple sources, etc., are all important ways to vet a source.
Vetting steps aside, it also helps to be aware of common forms misinformation can take. Knowing that pretty much anyone can create a website or doctor a photo, and that falsehoods can spread like wildfire on social media should give us a healthy level of skepticism. "The Sift" is a weekly publication put out by the News Literacy Project that includes helpful examples of falsehoods that have recently gone viral. Seeing real-life examples like these can train us to identify other fakes.
Credible sources can be shared with library users via the library’s website (with blog posts, book lists, etc.), programming, flyers, or even just in conversation at the desk. Navigating conversations is difficult and requires more than just knowing facts. We have to be good listeners and question-askers.
But as librarians, we do first need to be trained and informed ourselves about how misinformation spreads and how to evaluate sources using the already mentioned methods.
As far as helping the community, the approach will vary by the users’ interest level. Patrons that are aware of the importance of information literacy and the prevalence of misinformation might be interested in attending educational programs on the topic. For the majority of patrons, with either no time for attending programs or no interest in increasing their information literacy skills, they won’t be reached by programming. But librarians can still seek to pique patrons' interest or provide them with helpful information by posting flyers like IFLA's "How to Spot Fake News" Infographic. They might not be able to attend a program, but they might read a short blog post or watch a short video that the library makes available on their website.
Librarians also serve the community by determining what materials are added to the collection, vetting sources while being careful to not censor any one side (a task that is easier said than done).