There are two types of JW's, the smug, and the scared.
When an elder takes out a family to Dunkin Donuts, and the family looks relieved to be inside, while the elder looks "elderish", easy as pie. Whenever you see suits and ties at any fast food restararaunt, how can you not think of JW's?
The other dead giveaway is that most people in business suits are actually engaging in business. Thus, they are to themselves, in their own head, and aren't looking for anyone or any attention.
A JW in a business suit has head up, looking for someone to irritate and start a conversation with.
They tend to look like Outlaws Polaroid of a JW.... ;)