Courtesy of Club Med Sandpiper Bay

If winter weather has you thinking about a tropical getaway, a resort with a flat daily rate can mean major savings. But choosing an all-inclusive resort is trickier than picking a regular hotel.

On the upside, a flat rate can save you big money over paying for all your meals and activities individually. And paying in advance means less vacation time spent planning and more time relaxing. But many "all-inclusives" aren't all they're cracked up to be. Here's how to make sure you don't get nickel-and-dimed:

1. Size it up. What's your priority? A resort with more than 200 rooms will have more amenities—and is likely to be cheaper—whereas smaller properties tend to have better service and food.

2. Mind the "extras." Even at many all-inclusives, you may have to shell out for extras like golf, spa treatments, and off-property outings. To save up to 15%, try booking those activities in advance.

3. Comparison shop. Buying an airfare package from the resort could save you 5%, says Janet McLaughlin of Provident Travel. That said, always price flights yourself before committing.

If you're thinking about a last-minute spring break getaway, these three all-inclusive resorts offer sand, surf, and great value.