To determine a girl's TDM, one must talk to said female, stalk the shit out of her on facebook, analyze the way she struts, or figure something about her ability to, or lack thereof, wield a penis.
TDM's only apply to girls you would be willing to fuck. So, if there is a female that loves to gobble cock but is an absolute ogre at the same time, the TDM does not apply. At the same time, smoke-shows who avoid penis like it's the The Plague have a negative TDM which subtracts from her final 1 to 10 ranking. Therefore if a girl rated 6 has a TDM of +2, her ranking is boosted to 8. This means a male might find better luck hitting on the 6(2+) chick than hitting on the 10(-4) girl. Under this system, the hook-up culture is totally revolutionized.
Hot Girl 1: Oh no I don't like getting into those situations. I gotta go home with my friends.
**Hot Girl leaves**
Dude 2: Bro!! That girl was a smoke-show! You get with her??
Dude 1: Fuck her dude! She was like a legit 9 but her Taking Dick Modifier was like -4.