What is the best way to go about informing a prospective employer that my only work experience has been with my parents' firm?

@Mahilsen: In my opinion, your career pedigree is not only about where you worked (although clearly working at a really prestigious place can help), but also about what you did and how well you can communicate it throughout the job hunt. So the real key is to convey through your cover letter, resumes, and interviews what you learned, the skills you acquired, the experiences you gained, and the network you built. If you can effectively do that you'll be a fantastic job candidate, regardless of your family biz.

Now when it comes to dropping the "I worked for a family business bomb," you don't need to shout about it from the roof tops. You just don't need to shy away from it either. Perhaps there's an appropriate place to mention it in your cover letter... Or perhaps during your interviews, you can fit into your conversation the fact that your current employer is owned by your family.

Moreover, you can even discuss what you did in your question: it enabled you to take on more responsibility at an earlier age and you think you're in a better position to add value as a result of it.

In addition, some people might even respect the fact that you worked at a family firm. It isn't easy to work with mom or dad, but you stuck it out to gain skills and experiences, which is a lot better than sitting on the couch for the last few years - which a lot of people did. No one will ever knock you for working, especially in this environment.

Now I'm sure people would disagree with me. But like you said, it's apt to come to the surface, and why not get ahead of it. Otherwise, in your third round of interviews, when someone asks you whether or not you've been working at a family firm, be ready to nonchalantly answer, "yes," as if they're the only person at their firm who doesn't know that. (Clearly I don't really advise this.)