I'm at the Imagine Cup US finals and am among a crowd of people who are very influential -- congressmen & congresswomen, leaders of foundations and inner city youth groups, entrepreneurs, corporate VPs and more. It's a group that I am just fascinated to be around, because these are people who are making real change on a daily basis to make the world a better place.
When faced with a situation like this, one must draw upon the ancient art of remembering names. In an informal setting (e.g. a cocktail setting), business cards are infrequently exchanged. However, you often hear "Hi, I'm _____ from _____." Then, weeks later, you find a perfect opportunity to discuss a concrete, pressing issue -- or business opportunity -- with that person. You didn't get a business card; you can't remember the name; you are out of luck.
I've compiled a list of things that help me in situations like this.
In general, just follow the most important rule and you'll be fine. Listen to and be aware of the person talking to you. You never know when that connection could help you realize big aspirations!