Do a search of each destination your ship will visit. You can start with our handy port pages. Official local tourism agencies are a good place to gather further information on attractions and activities — some even provide handy downloadable maps, or will mail you packets of information if you ask them for it. 

Private excursion companies with a broad range of tours include ShoreTrips (shoretrips.com), Shore Excursions Group (shoreexcursionsgroup.com) and Viator (viator.com). Check them all to see if there's a better deal for a comparable excursion — you may find a wider range of options, as well as smaller group sizes. 

If you have specific things you want to do, such as renting a kayak or mountain bike or trying parasailing, contact local operators, check their prices, and make a reservation early. Keep in mind you could be disembarking on the same day as thousands of other cruisers, some of whom may have the same idea.

For a beach day, check the prices at resortforaday.com, which sells day passes to Caribbean beach resorts that give access to their pools and changing rooms. You can also reach out to hotels directly and ask for the cost of day passes and afternoon packages. 

On a lot of Caribbean islands, the best option is just to stretch out in the sun for the day on a sandy shore. Pick your beach in advance, get off of the ship early, and pack everything you need in your day bag — sunscreen, a beach towel, and bottled water — so you don't lose time shopping. 

Determine where you'll be docked and whether you can walk right off your ship to the attractions you want to see or if you need to take a taxi, bus, or ferry. Checking taxi fares ahead of time is highly recommended if you don't want to get ripped off.

If you don't want to get stuck in a restaurant designed for tourists, do a little research on the choices in port before you leave home. Some food lovers even design an entire day around a long, unforgettable lunch, especially in cities like Rome and Barcelona, where amazing restaurants are plentiful. Just be sure to make a reservation in advance if this is the center piece of your day.

You'll likely need local currency if you plan to take public transportation, visit museums, or eat in local restaurants. Not all attractions will take credit cards, and you don't want to lose time later hunting down an ATM machine.

If you're on an official cruise line shore excursion and run into traffic, the line will hold the ship for you if the coach is running late. That's not the case if you explore on your own, so plan to be back on board with plenty of time to spare.