It is vital to see all business entertaining opportunities as an important ingredient in the local business mix.
If you are unable to accept an invitation for whatever reason, make your apologies meaningfully and suggest another date. The importance of these relationship-building events cannot be overemphasised.
Detailed business issues are best left to the confines of the office. Use the meal as an ideal opportunity to broaden out the topics of conversation and develop your personal relationship more fully.
It is fairly unusual to be given a knife at mealtimes as the main implements used in Indonesia are a fork and spoon. Whenever eating, passing or receiving food, use the right hand as the left hand is considered to be unclean. (This rule applies even if you are left handed.) When you have finished your meal, place your fork face down on your plate and cross your spoon over it.
Indonesian food can be very spicy but less spicy alternatives are available. Ask you host for some local advice. It is polite to leave some food on your plate as a sign that you have been well satisfied with the amount of food provided.
Remember that most Indonesians are Muslims and may not, therefore, drink alcohol. Most Indonesians though (unless very orthodox) will not object to you drinking alcohol.
A gratuity charge of 10% is added in most good restaurants in Indonesia. If this charge has not been added then leave an equivalent amount.