Re: I wouldn't know what to say if the hottest girl in the world stood...
Why is "Hi" ridiculous?
The best and simplest opener is a confident "Hi, i'm <blah blah>, who are you?" while keeping steady eye-contact, because what you say is irrelevant, it's all about attitude. Don't think and open her spontaneously, as soon as she's there. If you linger and try to think of something perfect to say to her - you've already blown it.
Rarely used anything else, rarely had to.
If you like my advice, check out my dating blog at www.saulisdating.com/blog.html