How can they tell who's a Muggle?

Mon Feb 17 05:45:13 UTC 2003

No: HPFGUIDX 52357

As I'm re-reading GoF, I've come to a halt.  How can Wizards, 
particularly the DEs, tell who is a Muggle?  It can't be because they 
wear Muggle clothing because the Weasley kids wear Muggle clothes.  
The only thing that can give a Muggle away is if they speak to 
someone and show them their lack of knowledge about the WW.  Unless 
you're Hermione.  :-D

So does anyone know the answer?  Has this been talked about before?

Greicy