Laos is a very conservative place on a tight social leash. Education is low and generally people are not very worldly and are easily shocked. Dress modestly. You will see that people of both sexes dress conservatively, showing little skin above the elbow or midcalf. You as a foreigner can get away with shorts and T-shirts, but if they are excessively short or dirty you will garner a fairly negative reaction.
It's all about respect in the end. Avoid open displays of affection. The usual rules of respect for religion apply. Take your shoes off when entering a temple (and indeed a private home). Women should never make any physical contact with a monk. It is also important not to point the soles of your feet at another person and certainly not at a Buddha image. Never step over food or people. The feet are seen as being dirty while the head is sacred. Don't pat people on the head, even if it is meant as a gesture of affection.
The traditional greeting is called the "nop" or "wai," and if you can master it you will be considered very polite. You don't do it to waitresses or children. It is a sign of respect for your equals and social superiors. To perform a nop, place your hands together at chest level as if you are praying, bow your head to your hands, and your upper body slightly. In a business setting, a handshake is also appropriate. When you beckon someone, do not do it the Western way. Flap your whole hand downward with your palm flat. If you do it with your hand or finger pointing up, it is interpreted as either very rude or a sexual gesture.
As in neighboring countries, the concept of "face" is pivotal, and even if it means things take longer try and engineer things so that no one loses face. Lao people take a gentle approach to human relationships. A person showing violence or ill temper is regarded with surprise and disapproval. A calm approach will take you further. Patient persistence and a smile always win out, especially when haggling. It is important to haggle, of course, but just one or two go-rounds are usually enough, and no means no.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.