Club/party often.
More guy than girl friends.
Thot girlfriends (thots of a feather thot together).
If she entertains other guys flirting while you're with her.
If she refuses to let you use her phone.
If she is reliant on male friends.
If she let's you hit it on the first night.
If all her previous relationships were terrible +1 thot point for it never being her fault.
If she posts pictures that accentuate her ass/boobs on social network sites all the time
Permanently on the phone talking, instant messaging or checking social networks.
Complains about guys DMing her on Facebook. Doesnt disable DMing on Facebook.
Has over thousands of followers/friends on social networks when her accounts have little substance (ie. not a corporate account).
There is quite a bit more, just can't think of them now.