The opportunity for this doesn't come right off the bat. Usually, you should have established some rapport first and maybe removed her away from her friends. But, done right, it can be done even with a crowd.
Ask a girl things that will make you understand her better, like what makes her happy. Ask why that makes her happy. Make her choose between two different scenarios and challenge her beliefs.
And when you're somewhere more intimate, reference to earlier conversations. Or, if you manged to close well, ask if what you're doing makes her happy. Hehe.