Wow, this is a really good yet big question. Let me try and rephrase it a bit and dissect it into two questions.
1. How do I see the difference between “the hookup girl or fuck buddy” and “the relationship girl”?
There isn’t a difference. The difference lies in how you approach the relationship and when you give sex up. You can’t expect to have a relationship if sex is given immediately, however that doesn’t mean it kills those chances of happening either. The most important thing is you have to communicate (a) you want a relationship and (b) more importantly, understand that he does too, and actually believe it. You have to trust your gut – does this guy like you or does he just want to fuck? Does he talk to you about your life or is it always about sex?
2. How can you tell when a man wants an emotional connection and relationship rather than just sex?
Well, most “men” will actually say this: that they want a relationship and not just sex. The problem is, most men are not “men”. A lot of guys will say whatever they want to get you into bed, so the onus is on you to make the relationship bond happen well before the sex happens. It’s your job, if you want a relationship, to take it slow and get to know each other. Fall in love. Then have sex.
If you just want to hookup that’s fine too but it’s important that you make that distinction with yourself and him ahead of time.