Consistency and transparency
Getting someone to first Identify and even consider the worthiness of their source is the first step for me. Always ask where information is coming from and also tell or cite where you're providing information. The lack of personal responsibility of even knowing where you heard something or who you're sharing it from I see as a prevalent issue among people of all ages.
When working in a fast-pace and casual, public environment even I have to keep myself in check on where I'm providing a source from. If I get background information on an issue from a google search or a .com website, I try to find replicable information from a better source. If I don't find something because of a time restraint, I make it very clear where I'm providing the information from and how we'll both need to follow up to test the validity. I do this in library work and personal interactions to model good information seeking behavior.
A librarian's role is to model this behavior, promote this behavior, and demonstrate the important concepts of information literacy outside of charged politic issues. If the behavior is consistent, when the time comes to use the same practices in the face of volatile politic situations, questions, and assertions of false truths, we are ready, we are firm, and our reputation supports our actions that we are information professionals and our agenda is not based in personal bias.