That seems like a silly, question, right? But how do you tell if something is "accurate"? Here are a few questions to ask:
Where does the information come from?
Is the author citing another source/report/study? If so, try to look it up.
Is the information supported by evidence?
If the author is making an assertion, what are they saying to support their claim? Not sure about their evidence? Look it up!
Has the information been reviewed or refereed?
You've probably heard of "scholarly" or "peer reviewed" sources. This is the same thing. If your source is in a peer-reviewed book or journal, you can generally be *more* certain of its accuracy. BUT....
Can you verify any of the information in another source or from personal knowledge?
This is the thing, really, that you will need to do. Trust, but verify! If your argument is about something with which you're unfamiliar, then you need to do MORE research to make sure the content of your source is accurate!
Does the language or tone seem free of emotion?
An argument can be emotional, of course. But if your source seems "wild and crazy", you might want to think hard about the accuracy of the information being discussed.
Are there spelling, grammar, or other typographical errors?
These are signs of sloppy work. Sloppy work might indicate poorly constructed arguments, or ... you guessed it ... inaccurate information!
Let me mention journalism again. Major news outlets are generally accurate in reporting facts and the quotations they provide from their sources. This is because they are legally liable for how they report these things. HOWEVER, sometimes they can report things in a particular way in order to push one particular point of view over another.