We're exposed to so much information and so many different opinions every day that it's really easy to get lost in the details. Train yourself to learn which details matter and which don't.
Start by listening to your gut. If something doesn't sound true, that's your first warning sign. From there, you can start looking for other holes in an argument. Here are just a few ways to do that.
1) Think about who benefits from a statement
2) Question the source
3) Look for obvious statements
The more you pay attention to these kinds of details the more automatic your critical thinking will become. The end result is a brain that automatically forms better arguments, focused ideas, and creative solutions to problems.