Practice. The more you get used to talking to strangers, the easier it'll get
I like shy girl very much.
start trusting yourself.. think of "can do's" instead of can't..
Go to the top of a tall building with a megaphone and yell into it "I'M AWESOME!!!! I'M NOT SHY!!!! AND I'M NOT GONNA HIDE MY VOICE, I'M GONNA BE LOUD!!!!!" Or you could try talking to a therapist or someone?