Everyone's got their triggers. For me, it was that I always refer my mother to Snopes when she sends me one of these things. And I include the link to the Snopes page in the email. (Because she clicks links in whatever I send her, no matter how many times I tell her not to. And I don't want to have to explain again how to copy it to the address bar.)

So here's one that already has the Snopes link. "Hey, never seen that before. Maybe this one's legit ... Wait did I just? ... Dammit."