People in the US are allowed to vote simply by being a US citizen, registering to vote, and showing up. I think the bar should be a little higher for voting as it carries with it such large responsibility.
Civics. Every person voting should be able to tell you what a state senator and a US senator does. They should be able to tell what particular cabinet positions do, like the secretary of interior. They should understand the 3 branches of government and the system of checks and balances in place to regulate government power. I don’t know what the current numbers are on this, but I would bet they are staggeringly low.
Media Awareness. People should understand that even the most reputable news sources are subject to bias. They should learn how certain images and sounds are used to stimulate feelings in people like patriotism, excitement or fear. They should understand that statistics are often misleading or presented in a slanted way. They should know what propaganda is, how it has been used, and how it is used today.
Data Gathering. People should be able to fact check statements made by public figures without relying on talking points. People should show proficiency in checking sources of public information, and should ask for clarification and sources on dubious information.
Now some would say this puts a tremendous burden on the voter. That’s not really true. Most of this stuff could be taught over the course of a couple of weekends or taken online through correspondence. I’m not proposing that people know exactly how the government works, but they should have a rudimentary understanding. Democracy at it’s ideal depends heavily on an informed and educated populace.