Don't worry about it too much. Openers really aren't very important.
When you are in a creative mood, lots of good funny sh*t will just come to you. When you aren't, have a couple of default things just to get into set.
For example: "You look really Eastern-European".
I fall back on that one, whatever they look like. It just broaches the topic of geography, and the topic of herself. That's all.
I often transition to really daft stuff like her mum and dad (based on where she got those looks from), and other stuff that is easy to have fun with.
You'll also develop an eye, and start to notice things like fashion trends that girls use. And often be able to use these for a million opens. For example: the trend seems to be leather jackets and ripped jeans at the moment - worn by girls that don't have a clue about punk music. Accuse them of riding a motorcycle, or being a rebel.
Worrying about the open used to lead to me bottling out. It puts you too inside of your own head. Just come up with 2 that you can fall back on, and then get more creative when the mood takes you.
