I think by far the biggest threat is from the media. They've long since given up an pretense of objectivity.
To perpetrate a lie, the first thing they have to do is to convince you that all the other sources of information are lies, and they are the only ones telling the truth. I know people who firmly (and aggressively) believe this about their one favored "news" source.
You can still find the truth. There are plenty of legitimate journalists still out there. And plenty of biases.
One option is to read articles from sources on both sides, knowing their bias. Hear both sides of the argument, and learn the details that each side conveniently left out.
The other is to seek multiple, less biased sources. They do exist, and there are "media bias" charts available to help.
Any lies WILL be challenged by the opposing side, as well as by those without an axe to grind.
But if you only seek sources which agree with you, it's very easy to be fooled. And manipulated.