Wow, I didn't even pay attention to the days this was posted, and didn't realize it was necro'd. Dunno why the trolls constantly revive dead threads.
Anyways though, I came in to put in my voice in hopes it might help out some people, since obviously the friendzone is something a lot of guys still fear (and will continue to fear). Guys, you have to realize that girls (much like guys) go through phases, and not all of them will necessarily go through the phases in exact order, or go through all of the phases at all. So what I'm going to be saying is a generalization
girls of the age (since most friendzones come during [junior] high school and the early years of college at best), they're really attracted towards aggression, because on a biological scale, our bodies are still in the B.C. era. Our bodies are still worried about surviving a tiger, even if our brains are worried about buying the next iPhone. Aggressiveness is an attractive trait because it symbolizes a man who will protect the woman during pregnancy, childbirth, and raising said child til it can go and mate itself. Later in life, these women will most likely (but not necessarily) be more attracted to the traits you believe you have, such as kindness, being attentive, helpful, etc. because it shifts from the urge to procreate to the urge to settle down.
Also a lot of girls are attracted towards aggression because it's a sign of rebellion; something that's very big in the minds of a lot of teenagers.
However some girls don't go through this phase of aggressiveness and rebellion, are changed due to past relationships, etc. Some will genuinely be attracted to a guy like you. The most important thing to do is pull yourself together, muster up the courage to ask a girl out, and accept whatever her answer is. If she agrees to go on a date, try to make it a blast. Throw in some humor, pay attention to how the date is going (is she enjoying it? Does it look like she's just acting happy to get through it without depressing you?), and by the end of the date listen to her response. Would she like to go on another date with you? Did the two of you kiss (this isn't a deal breaker if she doesn't, but obviously if she kisses you on the lips, there's a good chance she's really into you)?
And if she declines, learn to get over it (I know it sounds harsh, but it's true), remain her friend, and try to muster up the courage to ask another girl out. You may fail your first few times, but the more you try, the more likely you are to get a girl who will like you and will want to date you. I don't mean ask every girl out, you want to make sure you are genuinely attracted to the girl you're asking out, but you will find there's a lot of potential mates/partners/etc. out there for you.
You may also find out the girl you first liked will like you later in life. Tastes constantly change, whether it's gustatory (that would be taste, as in food), auditory, visual, etc. And this does
include attraction. Just another reason to stay friends with her.
I'm not saying stay friends with her to possibly get in her pants, I just mean that if you'd stop being friends with her, your chances of ever getting with her would be close to zero. If you stay with her, she'll get to know more about you, and you may be the first guy she thinks about if she ever changes up her taste in men/changes them soon. So just keep that in mind.
Anyways, that's my two cents.
P.S. Please don't ever address yourself as a "nice guy", or any synonyms of nice. Thank you.