"Don't check you green habits when you check in," O'Neill said. Just because you might be staying in a hotel, you still need to remember to turn off the lights when you leave the room, turn off the air conditioning and not waste food.
Once you're there, walk instead of hiring a car. Check if your hotel has a shuttle or try public transportation. If you have to rent, ask for a hybrid. O'Neill also recommended Zipcar.
Reuse your towels and sheets whenever possible.
"Hotels use a huge amount of energy for laundry," explained green blogger Olivia Zaleski.
She also recommended letting your hotel know you're grateful they offer greener service and encouraging those places that don't yet have a re-use option to adopt one.
Think about your impact once you get there.
"Try to minimize extractive activities and emphasize ones that help bolster the local culture," said Paul Bennett, a founder of Context Travel, an environmentally conscious travel agency.
For example, eating at a small mom-and-pop establishment is much better for the local economy than going to McDonald's.
Once you're back at home, even if you feel you've treaded lightly, there's still more you can do.
"Offsetting your flight is a quick and easy way to green your trip," Bennett said.
The basic idea is to compensate for your carbon footprint by enabling an equivalent reduction in greenhouse gas by donating a carbon offset coupon. Options range from investing in wind energy to planting trees. Prices range accordingly depending on the scheme.
Bennett also recommended re-investing in your favorite destinations to ensure their future.
"Look for charities or foundations that invest in the place and medicate the impact of tourism on it," he said. "Make a donation, or volunteer to help on your next trip."