u can usually tell if a girl is into u...but being a girl myself i try to make it a lil obvious. If the girl looks into ur eyes alot that could b a sign. if she smiles around u alot,if she hugs u alot or asks for hugs(i kno i like hugs from guys i like), if she seems interested when u talk to her...there r so many signs..girls flirt in different way and thats my addvice. hope it goes well wit her..good luck!
2 b luvd