Boys and girls Advice please?

when i see this guy i like my heart beats like mad (i know all of below sounds like a cliche) we don't really know each other but whenever we see eachother he smiles at me and i smile back. but i feel like i have melted inside. My like...ermm... enemy asked him out because she knew i liked him and no im not lying cos we got in argument and she told me she was gonna ask him out just to rub it in. cos she is like drop dead gorgeous and slutty and i'm like normal. my mates keep saying he's not worth it if he accepts a date so easily but i really like him and can't get over him. past crushes for me were just thinking they were fit and going giggly. but he's different. i think about him and feel happy, relaxed kind of. and again i melt inside at seeing his face. he doesn't know but one) this girl is really pissin me off and two)i want to get to know him better what should i do?