Hey Pato
No I'm by no means an expert on picking up women, heck I'm still digesting all the stuff I'm reading and building up the confidence to finally go out there.
But what I can tell you is from my own experience. I used to be a "nice guy" in a sense that I would say yes to almost any request from a girl if I thought she was cute. A "nice guy" in that when a girl liked me, I would bend over back to do anything for her because I was sure that was the way to her heart. A "nice guy" in that I thought hooking up with women who weren't my girlfriend was wrong and immoral (the hell was wrong with me.) A "nice guy" in that I told myself I would wait months to have sex with a girl because it's right (though I was never able to wait that long, heh). Every friend who was a girl would tell me how sweet and nice and friendly I was, and I prided myself on that, really, because it seems like that is a rare quality to have. This was just less than a couple of years ago. Around the time I turned 21 I started acting differently because some girl tore me apart and the depression lasted for months.
I started not being nice to every girl I met just because I thought she was cute. Not that I was a jerk, but I wasn't trying hard show how much of a sweet person I was. For example, I would discuss on an emotional level things that would immediately reveal that I was an emotional person and, even worse, a hopeless romantic (blaghh). Like how much I wanted a girlfriend, how great I thought it would be, things like that. I would be sickeningly nice and supportive to someone I just met, which is a turn off. So that quickly changed. And now if topics did come up about past relationships and things that would naturally get me emotional, I would keep a cool head and talk about it without showing much emotion.
Also my biggest change was that I observed my best friend talk to the girls at college. He was the most charming person I met (half dominican half puertorican so it makes sense, yet physically he's not the best looking guy). The way he talked to girls and flirted with them changed the way I looked at how to interact with girls. I thought the rule was to keep classy, not flirt too intensely or sexually, and he made me see that that was absolutely wrong. Girls were laughing and had their attention completely on him because he did exactly that. And I know him best, he's my absolute best friend, and I know that deep inside he's sweet, romantic, and a nice guy too- he just doesn't show it right off at the beginning. And I think that's the key.
But I think it's important not to lose that part of you, ever. Because as far as relationships go, in my opinion, that's one of the best qualities to have, and it could also get you some great, caring women. My ex was an absolute stunner, educated, latina (my favorite), and had the most perfect body you could imagine. How did I get her? By being a gentleman, and being respectful, and almost no flirting, just deep conversation. I don't want to say by being a nice guy because, well, it has some negative traits associated with it, like neediness, etc. Many guys tried to flirt with her, pick her up, court her, and failed miserably. She told me all this, and told me that I caught her attention exactly because I wasn't hitting on her like all other guys. Not gonna lie, she did see me as a friend in the beginning. But she started falling for me once I showed my conversational skills and wit, and it helped that I was educated and had a passion for dancing. Always good to have =) then once in the relationship I was able to bring out my flirty sexual side, which she got used to and ended up loving. Maybe I got lucky, who knows. But at least I know there are gorgeous educated girls out there who like genuinely kind men.
Now, the other side of the coin. I met another stunner this past summer. I failed in the end with her but I had her wrapped around my finger for a solid two months in terms of who put in more effort and showed more affection (I wish I had found this site before, because then I wouldnt have become a needy punkass and would have moved muccchhh faster). At some point she was hinting at me hardcore to tell her I liked her, which I did, and she unleashed like a speech of how much she liked me and why. Now, what did I do with her to get her to like me? The opposite of what I did with my ex. Instead of having deep conversations in the beginning about our childhood and culture and upbringing, we talked about random crap, barely scratching the surface of who we were, but every conversation was dripping with fun and sarcasm which we both loved. I didn't know at the time, but I was almost a complete mystery to her (she told me this at some point; now I know its a good thing). And eventually, some sexual stuff got thrown in there. We would go salsa dancing and I had no reservations about dancing with other girls and I knew she could see. If I was still the nice guy I was before, I would have catered to her need the entire night. I know Chase mentions not to text much, but we would text all day, and sometimes she would stop but sometimes I would stop. But again, it was mostly with a sarcastic, playful tone, never kissed her ass once, never complimented her without her having complimented me first, always gave her playful shit to deal with. And, she mentioned, I was the only guy who ever did that; all other guys would break their back for her and kiss her ass. Sound familiar?
Then she went in for a kiss. I dodged it, but decided to kiss her back. Then I started showing my sweet side, which she adored and to be honest, craved. The holding, passionate kissing, the cute messages here and there. As I said, I had her wrapped around my finger, even then. But then I made the huge mistake of becoming needy after a few weeks, after her getting a 12 hour/day job 4-5 x week and having a new baby in the family. I was asking her too much to hang out, and asking her just
once why she was being distant. Once was too much.
Moral of the stories? Be sweet to those who deserve it, but don't be needy.
Girl #1 was an example of how being genuinely nice (and being able to hold conversation, and having value, duh) can land you an amazing woman. Girl #2 was an example of how I acted cool, suave, didn't kiss ass, and was apparently mysterious...and how I almost got the girl. Really. Don't be needy. Not even once.
So with that longass post what I'm trying to say is that you don't necessarily have to add bad boy qualities to yourself. Just try not to show your nice guy traits until much later on, after you've got some investment from her, because in most cases do it right from the start and you look like youre starving for a woman's attention. And don't be afraid to add some sexual references and jokes in your conversations with women. I think that'll take the nice guy image right off. Or, at least, make you a very unconventional nice guy, which is what I consider myself 
And in case you didn't catch it the last two times....don't be needy!
I'd go back in time and kick my own ass if I could
