Recycle and re-use everything possible. Stay on trails. Pick up litter. Don't feed animals. Consult a ranger for more ideas on what you can do to help national parks.
Many national parks are in some of the most remote, and sometimes harsh, locations in the country.
Be prepared for sudden changes in climate. Carry lots of water and high-energy snacks. Be aware of your physical limitations. Don't become a victim. Put your watch away.