How do you get a boy's attenion if you are shy?

Go up and talk to him! Get to know him better!

^^^ obviously thats not going to happen if u r shy.... just try to get to know him better, but slowly. start with a smile one day, a hi the next, or maybe just asked him for "help" in class..... just find a simple excuse to start talking to him nd b4 u kno it, you'll find the perfect opportunity to flirt or become friends. then this will gradually lead to something more!

Or just go up to him and be like hey you, yeah you i like you, bye. and then disapear