when is it time to decide if you are interested?

Okay, when out 'dating' when is the right time to decide when someone is not right for you?
It would seem from some of the comments on this blog and men I have spoken with about this is right away--- it seems men seem to know 'right away if they want to do a woman.' So that is the reason they would ask a woman out again.
Back to school again.
I guess many women agree- BUT that is just to have sex--- it does take longer to decide if someone is a person you want a relationship with and that takes time.
So, women I guess should not go out for a second cup of coffee with men unless they are attracted physically--- and if you are attracted to him- but not sure if you want a relationship with him you should NOT go for a second cup of coffee as he will think then you 'want to do him.'
Jessh- boy am I glad I am single- thought the sexes were closer than this!
Cause if you don't want to meet him in private after the first cup of coffee in public ( and you do not know who this person and have never met him before- do not worry about your safety- just agree to meet him in private anyway-- JEESH--- isn't this what happened to a man that met a 'woman' in her garage and got cut up?)
aughhhh-- I think if a man is not interested in how you feel and your sense of safety he is not worth having a second cup of coffee with- cute or not!