Before you fill out your credit card information and click "book," ask your hotel, lodge, or tour operator some open-ended questions. "Even if they don't have an answer, it sends a message that this is what travelers want," says STI's Mullis. You'll create awareness of growing consumer demand for sustainable tourism—and maybe even get businesses to do their part.

The five questions

1. Do you have an overarching sustainability policy, and if so, where can I read it? (Most organizations keep this information on their websites.)

2. How are you supporting environmental conservation and stewardship both globally and locally?

3. How are you supporting the local cultural heritage?

4. How are you supporting local economic development and ensuring that your workers are treated fairly?

5. How can I verify that your policies are legitimate and practiced to the greatest extent possible?