Think about something you know a lot about, i.e. something you have a bit of expertise in. How do you know when someone you're talking to about this topic knows what he or she is talking about?
How is your judgment different when you're hearing someone talk about something you don't know much about?
The best ways to ensure that your information is accurate is to:
1. Verify the information -- if you find information from a source or website whose quality is in doubt, go to a reputable source you're familiar with or to a database to find information that supports or refutes the the less certain source.
2. Triangulate the information -- if you come across facts or opinions that are controversial or in dispute, look for three or more sources that corroborate the statement or idea.