Most so-called sustainability "certifications" are self-policed. If sustainability is important to you, and you aren't equipped to conduct your own inspection, look for a credential that is verified by one of the following certifying bodies:
• Green Key Hotels (greenkeyglobal.com) offers a key rating of one to five, based on nine factors (e.g., energy conservation and indoor air quality). It lists hotels in the U.S. and Canada (and several properties in other countries).
• Sustainable Travel International (sustainabletravelinternational.org) offers a STEP certification that certifies cruise ships and shore excursions, as well as hotels. A list of certified members can be found here.