Surprised no one has mentioned that Naples is a pretty scary place (and I'm a city kid). Twenty-plus years of world travel and my wife and I still remark about Naples as the most uneasy time we've had. Even our relatives nearby arched their eyebrows when we said we were staying there. I wouldn't spend more than a night there for pizza and Pompeii.

If you're a first timer, my suggestion: buy a guidebook and take some time to plan around what you want to see and do. People here can give you advice on specifics once you narrow down your preferences but I wouldn't rely on the subjective opinions of others to plan the basics (cities, nights in each etc).

For reference, last visit we spent 15 nights total and did: 3 in Sorrento to chill out; 2 in Naples to see family; four in Rome for the sites and the Vatican museum; three in Venice; and two in Trieste to see more family sites (the last night was in LON on the way home). Flew into NAP and out of Trieste. Bus from NAP to Sorrento. Boat from Sorrento to Naples. Trains the rest of the way It worked for us. Our trip next summer will probably just be ROM as a base with day trips south on the train. YMMV. Good luck and enjoy.