I tend to know from the start whether I'm attracted to someone or not. I've tried to "let it grow" with a few guys who had winning personalities, etc., and inevitably the more time I spent with them, the more confident I was that I just wasn't attracted.
I think an important part of dating is learning yourself, and how you react to other people. Cmego and I (for example) are really different in dating, not better or worse, but different, and I think for both of us, learning our own habits and patterns, like when we sense attraction, helped ease the process, because as you move into that "dating self awareness", you can trust your gut more, and know what you need to look for, what works for you (even if it's different from everyone else you know).
Most of the bad dating advice I've gotten has been trying to convince me that I need to behave in a way that is personal to the person giving the advice, instead of to me.