Anytime you approach a girl it is in public unless you approach her in your bedroom, at which point, she already wants to take her pants off. You don't need a line; you need intent. Not sexual intent. Intent on making her reveal something interesting about herself (hook) and then rewarding her for it (line), and then sharing something personal about yourself (and sinker)..
1st ex, (6 years) I was cheated on by her and a close friend. She had a kid who she gave my middle name to and raised for awhile as my own. She left and never let me see him again..