Lots of people are not grifters.

But if someone is selling politics or religion (or even worse, both), they are likely a grifter. People who sell outrage, likely a grifter. People who make money off of political office or religious position, grifter.

This is a decent start of a list. It's not hard to spot.

Lawyers making money off the misfortune of others, grifter. Maybe ambulance chaser.