How to do Naples in one day? What are the best things to highlight?
Take a tour on the HOHO bus, the one ticket buys you 3 routes http://www.city-sightseeing.com/?command=search&clear-search=true&destinations=Naples
Robyn, I see that you're asking some fairly basic questions about traveling in Italy. Good for you for doing some research, but I have to highly recommend the Rick Steves Italy guidebook because it will answer these questions and many more that you will have. For example, his section on Naples tells you exactly how to do a daytrip from Rome. Happy travels.