What’s the most sensible way to certify sustainable hotels? Tourist destinations often have little in common with one another but a penchant for attracting Bermuda-shorts-wearing masses. Are travelers—and the rest of us—best served by a standardized system, or would regional models be more useful? Some programs emphasize physical factors like architecture; others focus on service issues, such as the use of biodegradable cleaning products and local, organic foods. Here is a look at how the most prominent and promising certification programs address these questions.