Nicole Markle at the Allstate Blog suggests you develop a quick "about me" script so you always know what to say.

Practice your script before you go somewhere where you know you'll meet new people. Make sure it's not just a one-liner, either. For example: instead of saying, "I work in IT," say, "I do IT work for That One Company over by Landmark. I focus mostly on solving software problems and keeping things running smoothly." Be descriptive about what you do, and it never hurts to mention how you help people instead. The more easy-to-understand information you can provide in a brief amount of time, the more likely they'll be able to ask follow up questions and get to know you more.