I think there is a lot to be said about first impressions, so making yourself look good and having a friendly greeting with somebody goes a long way.
You can generally talk about many things, as long as it's not, you know, a turnoff or offensive.
I sometimes tell guys to make it a point to know what color her eyes are. If you make a point to recognize what her eye color is, it means you've looked her in the eye.
Your best hope is to be honest with the person. Admit you were just trying to make a good impression.