Ben,
This is a very difficult topic, being a junior in High school is a very hard age. And, the situation that you described is difficult, hopefully my advice will help.
The most important thing that I can stress to you first and for most, is to get to know yourself. Neil Clark Warren wrote a wonderful book called Two dates or less. Which asks questions like, what is the most important thing to me, who is the most important person in my life, what are my interests, etc.
Okay, once you have those figured out get involved with as much extra curricular activites are you can possibly handle. Join as many clubs, and be yourself around this girl that you mentioned you had an interest in. Being yourself is key, because otherwise they really do not know who you really are. And, you want to them to know who you are, because you mentioned you are a nice guy, and you want this girl to see that.
I hope this helped.
Denise
