Red flags:
Enjoys blood sports of any kind (instant deal-breaker)
Has never lived alone as an adult (he might have no experience of looking after himself and doing his own housework)
Doesn’t take responsibility for his own actions
Doesn’t apologise
Frequently comments on other women’s perceived attractiveness (or lack of)
Makes jokes that belittle one person in front of others (they are often small, seemingly harmless jokes, but unless they’re an in-joke between close friends, they can show a need for control)
Talks about how wonderful his ex was (who left him)
Talks about how awful and crazy all his exs were
Is generally indecisive - not as in, “I don’t mind, what would you like?”, but as in dithering endlessly and failing to make any decision at all (yes, I dated him and it drove me mad)
Green flags
Is kind even when he thinks no one is watching. I personally like a man who’ll stop to right a beetle which is stuck on its back, or rescue a bee from drowning in a pond
Is reliable and keeps his promises
Looks and smells clean
Sees his kids often (if he has them) and is a hands-on parent who takes on his share of the mental load