Beware: More Possible Scammers Going Door to Door

Some of these incidents have to be legitimate, no?  These scammers are really going to make it difficult when a proper solicitation occurs…  So how do you separate legitimate requests from scams?

Dear PoP,
Yesterday afternoon a woman knocked on my door.  She did not identify herself or her address but pointed vaguely saying she lived 5 houses down.  She said a relative of someone in the neighborhood was diagnosed with diabetes and she showed me a dog-eared high school photo of a teenager.  She said she was collecting for a fund for him.  I politely said I was not going to contribute.

I called 311 and told dispatch about it and asked that they drive down the street to let the woman know that her ruse made me think she was casing the area for future mayhem.  I do not know if they did.