Email communications.
First of all I have different email accounts.
I never give out my real email address.
I will begin to correspond in-depth to learn as much as I can about someone with one of my different accounts.
I then maintain a message history and if a flag raises, have it available to make comparisons against.
If I spot an inconsistency, depending on the severity and my feel of the person, will either call them on it or decide to discontinue the interaction.
(You will also find there are indeed plenty of fish in the sea.)