this is how i approach girl in club:
1 - start to bio her from far.. and let her know ur attention is on
her.
2 - if she didnt move away, it usually means she want u to look
longer on her.
3 - start to dance near her, if possible beside her..
4 - if she didnt even swap places with her friends, then dance with
her
5 - if she let u grab her waist, likely she's yours.
*but there are instances when the girl is just looking for a dance
fling. so, she'll happily walk away after a dance or two.
bottom line is, if u are gd enough, there are 101 ways to approach
that girl, any way will do if she is interested with u. if she
ain't, even a casanova wont help.