what is it that makes a girl want to be in a relationship?

This really bugs me, I feel like I do everything right when it comes to girls, I be extremely nice, and they usually say im really cute, or funny, and pretty much seem to like me. My problem is that every time that I try to get close to a girl, or tell her i like her or something, they say they just want to be good friends....
I feel like other people do it so easily, just ask a girl out and they say yes. I dont know if its my approach while talking to them, or the way i tell them that i like them, but girls always seem to say thie same things.

I am wondering, what do you girls think when a guy asks you out or tells you that they have a crush on you? what makes you wanna say yes to certain people, and no to others?

Maybe you're trying too hard.

Maybe it is the type of girls you are going for? Maybe try expanding your horizons and see if you click with other females that you generally don't think you would. There is also such a thing as being too nice (could come across as a bit desperate) and like Spring said trying too hard.
As for answering your question what makes you wanna say yes to certain people, and no to others? I think it is just a matter of feeling that connection with the person asking me out. You know pretty much straightaway if it is someone you want to get to know further.
Age has something to do with it too. I tend to go for the nicer guys now whereas back in my teen years I tended to like the dickheads. Don't know why... probably more a reflection on how I felt about myself more than anything else.

There is am endless list of reasons why she might want to be just friends. Can you afford to have a girlfriend? Do you know how to lead and initiate? Bottom line: You have to show her you are an alpha male. I have given up on guys before because he just wasn't showing he can be a man. Have you ever wonder why there are so many unattractive men with a girl in their arms? It is because they know how to be an alpha male! He is willing to do what it takes to have her. He would cover the tab (show that they are dating not just friends), he isn't hesitant to hold her hands and take the lead to go for the kiss, and is persistent until he gets her.

Well, if a guy told me he had a crush on me, I would feel really awkward. I mean, what am I supposed to say to that? If you like a girl, just ask her out, you don't have to explain that you're asking her out because you have a crush on her. That's a given.

Now, as for the girls who reject you, they're probably not attracted to you or they don't feel much of a connection. I always go for nice guys, but there has to be physical attraction too.