First of all look at the destinations of the excursions of your cruise line then check out other cruise lines excursions in the ports you are to visit, you’ll find their excursions on their web pages. Then look at the “Virtual Tourist “ site and “tripadvisor” and read the best things to see and what dangers to avoid. Write a list of those things you would like to see and do in each port or go back to your cruise’s excursions and sort out the best things to do (it may be a selection out of two or three of their tours). Then if you still have time look up each port’s tourist site on the web and copy and paste any really interesting information like maps and timetables of trains and photos. You are now in a position to make good decisions. Finally try to get some other passengers to enjoy they fruits of you labours (and spread the cost of a taxi ).
It is like driving….when you know the roads is so much more pleasurable…Good Luck Neil Down