They prefer the "Star Wars" prequels over the original trilogy. This is disgusting, purely and simply. If ever there was a way to root out the infestation of demons on this planet, it's asking someone which "Star Wars" movie is their favorite. This'll save you a lot of time.
They're always boring as hell. They don't have a unique bone in their body. Day after day, they slump through life like boring sheep in a herd of likeminded mammals. Everything about them is predictable and unchanging, and they show no signs of ever wanting to change.
They never pay attention to you. When your partner is more interested in their computer or phone than being with you, then you need to rethink your situation. This person obviously isn't feeling whatever it is or isn't you two have. There are people out there who will definitely give you the time of day. Maybe give them a shot instead.