you can use indircet opener's to sets if they were in a buss , if you used the direct opener it wouldnt always work , its not like your trying to approach , but when you use an indirect opener , you get a chance to sit and talk to her as if you wanted to talk to someone , try it on sets it would work , and if there was a girl alone , she would probably be bored and would appriciate you talking to her .
try it , even if you got rejected you will still gain experince , its better than sitting doing nothing , atleast you will learn
and rember to think positive , dont go like what if .... what if ... , just go and be confident and relaxed and you'll start to get results