IF you have nothing to back up your comments, just make stuff up, it's not something I do but the best arguing friend I know (total tosser) makes up stuff on the spot, very impressive and hard to argue with!
I just try to know as much as I can, it makes my opinion easier to back up
You have to make up stuff nobody would know and is difficult to find out about! Or just do a bit of research! It's very difficult to prove something wrong, once somebody says "this statement shows 8 million letters are lost by the RM each and every year" it's very difficult to find a statement which proves otherwise, whether it's true or not (which it is!). You have to take the position of control.