This isn't as easy it sounds. For starters, you have to learn how to distinguish red flags from mere quirks and annoyances. If a woman on her first date with you wears an orange-striped top and you hate orange or stripes, this is not a reason to bail. If her cell phone rings during dinner and she takes the call at the table, this is annoying—to me, very annoying—and will need to be addressed at some opportune point (not the first date). But it's not a dealbreaker. If, however, you take a woman to a restaurant that serves fancy pizza, as I did once, and she eats the pizza by scraping the cheese and tomato off the crust, leaves the crust on her plate, then lights a cigarette, smokes it, and grinds the butt out on the crust, this is a red flag.
This really happened, by the way, and if you work for a fashion magazine, you know who this was, so I'd better not say more.
A thoughtful reader may have already concluded that the greater challenge of red flags is their subjectivity. Another man, that is, might have yearned to provide the fathering that D—'s children so clearly needed. Or have been charmed—even turned on!—by the grinding of that cigarette butt onto the pizza crust.