Don't take it with you. That driftwood on the beach or hunk of washed-up coral may seem harmless to take home as a souvenir, but imagine if everyone did the same thing. That starts to change the entire ecosystem. Don't do it.
Carbon offset. If you're flying to your destination, consider flying with one of the 30-plus member airlines of the IATA around the world that offer carbon offset programs. These help neutralize the airplane's carbon emissions by investing in carbon reduction projects like tree planting or wind energy investments.
Eco-friendly rides. If you are taking a road trip and your car is a gas guzzler, rent an eco-friendly hybrid for the journey. These use less fuel than a regular car and also produce less carbon emissions, thus reducing your footprint.
Use a water filtration device rather than plastic. If you're traveling to a region where the quality of the drinking water isn’t reliable, instead of using dozens of plastic bottles, bring your own wide-lipped water bottle and a water filtration device like the SteriPen Adventurer. It’s lightweight and uses UV light to purify a liter of water in about a minute, which you do simply by stirring the device inside the filled bottle.
Bring eco-friendly soaps. If camping or staying in hostels where you'll be doing your own dishes, bring eco-friendly dish soap. This ensures you don't pollute the water with non-biodegradable washing products.
Be green in the hotel. If you're staying in the United States you can check if a hotel has LEED certification before booking—try to stay only in the properties that do as they have been recognized for their eco-friendliness. Regardless, there are steps you can take to be sustainable in a hotel. This includes turning everything off when you leave—lights, air-con/heat, and TV—as well as not having your towels laundered each day.
Privacy, please. Take the above to the next level. Opt out of the housekeeping service at hotels by leaving the "Do Not Disturb" or "Privacy" signs on the door for your entire stay. This will keep your sheets from being washed unnecessarily or your floors being vacuumed, both of which cause energy to be wasted.
Respect wildlife. This is especially important when hiking areas rich with wild animals. View that grizzly bear from a safe distance rather than edging in looking for the perfect Instagram. Not only do you risk getting mauled (or worse), but if you do, the bear will most certainly lose its life for your stupidity. Wild animals are wild. Keep them that way.
Pick up trash. Not only should you pack out your own trash when hiking or backpacking (obviously), but also bring along an extra trash bag and clean up any garbage you see on the trail along the way. You'll be paying it forward for future hikers and helping sustain the environment. Now that's something you can proudly brag about on Instagram.
Live local. Connecting with new friends is another way to feed your mind on the road. Eat your way into the heart of a new culture with EatWith, which allows home cooks around the world to invite you in for dinner. Want a truly local guide? Vayable and even the new Airbnb Experiences pair travelers with locals who have similar interests.