I've only been on two, so I am no expert . . .
- Don't book excursions through the cruise line. You will find far smaller crowds, better "tours," more authenticity, and far lower prices booking through an excursion company yourself. Better yet, do good research at each location, determine what you want to see, and explore the islands on your own. Most of these excursions get kickbacks from restaurants/touristy things for bringing crowds there every day. They aren't necessarily taking you to the best things to see/eat/do, but rather, who gives them the best kickbacks.
- If you rent mopeds/cars, be smart about how you pay (credit vs. debit card, cash, etc.). Be sure to take pictures all over the inside and outside of the vehicle before you get it and when you return it.
- Wake up early. Most ports take place early in the morning. If you wake up a bit late, you may face a wait getting off of the boat. Worse, you will wish you had those couple of extra hours you spent sleeping to explore more of the island.
- Do your research on tripadvisor for each location. Have a thorough idea of what you want to do/see. If not, you will spend hours asking about things and trying to find things. Have a backup plan - if you plan on spending a day on the beach, have other ideas in mind if it rains that day.
- I agree with BC and have no idea how Herdman could have felt like he was sitting around all day. If you go on a shorter cruise, you usually won't have a full day at sea. You'll board and have that night to get used to the boat (check into your room, explore the boat, have dinner, go to a show/shop). By that time, it will be later in the night and you'll want to be sleeping. The next morning, you will be at a stop. If you get off of the boat in the morning, you will have about ten hours to explore the island. If you get back on the boat around 6 pm, you guys will want to shower and go to eat. By the time you are done with that, it will be around 9 pm. If you watch a show or do anything else for an hour on the boat, you will then want to be back in your room around 10 pm or 11 pm. At that point, you will get 7 or 8 hours of sleep and want to wake up again to go explore the next port.
I really can't understand Herdman's feeling about sitting around at a hotel unless he was on a long cruise which had multiple days at sea without stops. I was on a 2 night cruise and a 3 night cruise. I think the perfect length would have been a 4 or 5 night cruise, which would probably include one day at sea without stopping (which would make for a day of "sitting around like at a hotel," which would be a nice break after having three or four stops).