In some of the temples entrance may be prohibited for non-Hindus.
Leather articles are prohibited to be taken inside the temple precinct.
It is better not to touch offerings or persons when they are on way to shrines.
Beef is strictly prohibited among both Hindus and Buddhists.
Walking around temples or stupas is traditionally done clockwise.
It is advisable to ask the authorized person before taking photograph of temples, stupas and monuments.
Social tips:
It is better to be decently clad when visiting any place. Sun and beachwear is not proper when roaming around. Briefs, shorts, bare shoulders and backs may not be appreciated.
Do not be offended if a Nepalese lady hesitates to shake hands. In Nepal, especially women, do not normally shake hands when they greet one another, but instead press palms together in a prayer like gesture known as "Namaste".
Public display of affection between man and woman is frowned upon.
There are strict rules on drug abuse; trafficking and possession of drugs are taken as serious offences.
Cheap charity breeds beggars but does not solve their basic problem. Therefore, do not encourage beggary by being benevolent.
Some other Important Tips:
Beware of touts who claim to be representing companies and offer to take you bargain hunting.
Use hotel safety boxes for your valuables. Do not leave cash and other valuable things lying around in the room.
Table manners in Nepal are quite different from those at home. In typical and traditional Nepali houses, plates, knives, forks and spoons may be absent from the dinner table. While eating, Nepalese people use their right hand. But this does not mean, however, that the guests are not to use forks and spoons.
Any food or utensils touched by the used knife or spoon or finger or lips or into which spittle has fallen is considered "Jutho" which means, "contaminated". Nor should the dish containing such food be used again without it being properly washed.