Apart from the beaches and scenery, temples and festivals, Bali's chief attraction is the Balinese themselves. Throughout the centuries, they have perfected the art of receiving visitors with grace and hospitality. Conversely, they have also excelled at repelling enemies, drawing on vast reserves of pride.
Do not be alarmed or offended if people that you meet immediately ask a bunch of very personal question. This is simply polite small talk in Indonesia and, in most instances, detailed answers are not required. All Indonesians have a documented religion, and may not understand many visitors' reluctance to discuss matters of belief. In the interest of social ease, some travelers of less traditional religious views will choose a major religion most compatible with their personal beliefs, so as to have a ready answer for the inevitable question.
One of the joys of traveling is meeting new people, and experiencing a different culture. Most Balinese people are happy to discuss their culture with you, if you demonstrate an honest and open-minded interest. Language barriers can be frustrating and, if possible, it is well worth it to learn a few phrases of Indonesian. Bali has a very non-confrontational social system, and giving rise to frustration, raising one's voice, or getting visibly angry or upset, will generally not get the desired results.
Indonesians, like most people, pride themselves on treating guests well. They will notice and judge the ways in which your customs and habits differ from theirs, but make many unspoken allowances for foreigners. However, there are some local mannerisms that should be observed. Do not pat people on the head, the top of the head is sacred and not to be touched. Try to give and receive with your right hand, most Indonesians perceive the left hand as unclean. It is impolite to point, and if you want to beckon someone, such a waiter or taxi driver, a downward motion of the hand is preferable.
When shopping, please do not tell a vendor that you may come back later. Although this may be meant as a polite brush-off, many Balinese will take it literally, and wait for you. Remember that you may be perceived as a very wealthy person. Most of the people you will have contact with have never traveled abroad, as you are doing. Generosity is very much appreciated. This does not mean that you shouldn't bargain, by all means you should! However, on those occasions when a reward is appropriate, give one.
Practice common sense as you would at home, and be open and friendly. Your time in Bali should be a magical experience you will treasure forever.