CART was a consultancy business that Roger Millman ran for a while
to encourage people to travel more responsibly.
He put together some guide
notes for responsive travel including a
Credo for the Caring Traveller. They can be found here.
Towards the end of the 20th century he wrote a short book
called Signposts to Responsive Travel.
The content is a somewhat dated now but many of the principles still
apply.
Click on the icon to read as a single PDF 
or pick an
individual chapter from the contents list below:
CONTENTS:
1. TOURISM AND THE DEVELOPMENT DEBATE
2. TOURISM TODAY - SOME CULTURAL INSIGHTS
3. PARADISE LOST - THE CAUSES AND CONSEQUENCES OF SPIRITUAL EXILE
4. EFFORTS TO RECLAIM LOST INNOCENCE
5. HERITAGE AND THE QUEST FOR SUSTAINABLE TOURISM
6. TOURISM REDEEMED - TOWARDS MORE THAN PARADISE RESTORED
POSTSCRIPT: SOME SIGNPOSTS TO RESPONSIVE TRAVEL
Some links to related organisations can be found below: