When you are in a nature area - either a protected area or any other nature enviroment - do not cut flowers or branches and do not take any plants out.
Stay on the paths and trails and try not to make too much noise - remember, in the forest you have to "look with your ears".
Clothing should be dark.
Do not touch animals or feed them. If a guide or other person is doing so, you should object.
Camera Flashlights (or torches at night) are very harmful to animals.
Do not enter nature areas with motorized vehicles; even on horseback, this should be avoided.
Please Pay all entree fees, since this money is more then necessary for the protection of these areas.
Support projects such as "Adopt a Turtle" or similar initiatives: in most cases theseorganizations carry out important work.
Never buy souvenirs which have been manufactured completely or partly with materials of endangered species (crocodile leather, for example).
Talking about the enviroment in general, we think first of all those practices we all know: do not litter and recycle where ever possible
Cigarette buts should not be thrown on the street and even less near nature areas - not only for danger of fire, but filters are a problem, too.
Save energy where ever possible and NEVER leave an airconditioning running when you are not in your room.
Electricity saving bulbs do not provide a cosy light, but are necessary energy saver.
Apart from those issues you should not do, there are many positive attitudes that may support sustainability
In restaurants ask for organicly grown food and judge any public place on the fact how "green" itis, not only in terms of environmental protection, but also of labour conditions and personnel involvement.
If you think buses exhausts are producing too much smoke, make your complaints. Be critical, and major enviromental pollution should be made public using internet or local channels.