LPT: If someone says something you know is wrong, don't automatically try and give them reasons why they're wrong. Rather, ask them to prove their point to you and then defeat the reasons they give.

This way, you'll force them to defend their argument (as they should since the burden of proof is on the one who proposes the argument) and know when they have no supporting evidence.

Also attacking an argument is a lot easier than defending one.

And lastly, watch out for people who try and get out of having to support their points by saying this like "just Google it", etc.