CruiseTip: Always be sure what time the ship is leaving and if local time is different than ship time.
When travelling in a group - set clear expectations of how much time you will spend together each day before you leave. No fun arguing in the middle of Rome about who's going to dinner.
Consider bringing clothes you could leave in the hotel along the way. Smaller luggage and more room for souvenirs.
Consider packing socks and underwear in gallon size ziploc bags. It'll be easy to tell which are clear and which are dirty.