i think that rubbish subs are those that look only to meeting their own needs and sexual appetites. there is an almost frenzied pace to the way they engage and approach a Dom/me. the needy, clingy, whiny, bratty and overly dramatic attitude that they display. everything is about "me."
a true submissive everything is about "Him/Her." your desire and passion is to serve, please and obey your Master/Mistress. in doing so you find your own personal pleasure and enjoyment are fulfillled. Their pleasure is your pleasure. your goal and desire is for the mutual connection and amazing feeling of sharing the exchange. not just getting your own needs fulfillled.
i think some of the warning signs of a "wanna-be" sub are:
1. changes Master's frequently
2. seek and need constant attention
3. "all about me" attitude
4. jump into play connection or relationship
5. don't invest in their own personal growth
in my opinion a true subissive is one that sees their service as a gift and desries to give it to the right one freely. spirited and intelligent without that "i can't be tamed" attitude.
"high maintenance" subs are like a bad car. you spend more time with them in the shop "fixing things." you don't really get to enjoy the wonders of driving on the open road.