Can someone explain this to me?

im 15, in grade 10, im a guy, and there is a girl i like however im not good at making and or starting random conversations.i have also realized that i lack confidence in myself, im shy sometimes, and i am an indecisive person. i play b guitar, electric guitar, and drums.i am average looking, im like 5"10, my hair is between light and dark brown in colour and its sort of longish but more of a shortish-long style(lol i dont blame u if u get confused by that), and i have green eyes.i guess im more of an introverted person but im quickly becoming more extroverted(i mean that im not the type of person that would go and arrange for his friends to all go to the movies or something.im more of the kind of person that will go if hes invited but will inquire about it as well).sometimes i think im good looking or whatever but other times i dont.i kind of got off topic but my main point was that i dont have enough confidence in myself when it comes to talking to girls and i want to change this.so can anyone give me any tips on how to be more outgoing?and things to say to girls like how to start a conversation?also how can i tell her that i like her without sounding insanely awkward?i know that all the confidence in the world would not make me be able to tell her without it being a little awkward.i think she might like me a little but the probability is close to around 17%.also i get kind of nervous when she is with her friends so more often than not i dont go up and talk to her.so yeah all ure opinions on me and on my situation are helpful.to sum it all up, i want to know how to gain confidence when talking to girls.