Information interviewing is one of our top ten recommended ways to learn more about jobs or careers that interest you. It fits in with Step 3 of High-Quality Decisions: to learn more about your career options.
For more practical advice on how to set up an informational interview, I highly recommend the last chapter of Roadtrip Nation: A Guide to Discovering Your Path in Life called "Do it Yourself: How to Set Up Your Own Roadtrip Experience." I've read a lot of career advice books and this one offers very practical ways of handling "cold" calls or emails. Plus it has great interviews with lots of different types of people that will inspire you.