Cambodia is a very traditional society which is strongly governed by traditional family values and Buddhism. It's much recommended that the foreign travellers in Cambodia know and respect the Khmer culture while wandering in the country.
Traditionally the Cambodians would greet each other in the position of holding the hands together like praying, bowing slightly to each other. Nowadays young people would also greet each other by shaking hand, but the traditional way would so much of mutual respect.
Traditionally both men and women in Cambodia would wear sarong, even though Western-clothings are more encountered while you are travelling in Cambodia. When you visit a Khmer family or pagoda, it's recommended to have proper dress which should include a sleeved-shirt and long pants. Wearing tank tops and/or shorts is not recommended when visiting pagodas and holy places. When entering a house or pagoda, it's recommended to leave your shoes outside if the locals do so.
When eating at a Khmer home or praying at a pagoda or temple, the Khmer would sit on the floor or mat with the feet to a side.
The Khmer gives a lot of respect to the royal family and it's recommended that the travellers don't show any negative attitude towards and disgreement with the royal family while in Cambodia.