How do i to talk to a girl on bus?

[664]

So there is a girl i like on my school bus who i see everyday and i think she interesting in me . On the bus she doesn't really stares at me as much (although we had some 3 second eye contact sessions) but when i get off the bus and look up her window seat she is always staring me (today she smiled a bit)
She's been on my school bus for a year or so ( she sat a couple of times next to me but nothing really happened) but I've never found the courage to make a move (i'am shy and talking isn't one of my ups) I'm not sure if she actually likes me.(btw a girl liking me is a rare phenomenon->i am not that handsome) I've recently added her on Facebook and according to it she is single . She talks and hangs out with older and bigger guys and that keeps me a bit worried to if she really wants me (i am regular to skinny size )
Anyway you could advice me would be appreciated , thanks

P.S. I am almost 17 and she is a couple months older that me , i'm 70kg and 175-180cm or 155lbs and 5.8ft