7. He Only Flirts in Private
Some people are just shy, but you should still be cautious when someone only flirts with you on the phone or when you're alone together. If he doesn't want anyone to see how close the two of you are, he might be doing the same thing with other girls.
Flirting can be harmless, as long as you don't break any hearts. Are you wondering if a certain someone is interested in you or if they're just flirting for the fun of it?