When attending normal business meetings, standard western business attire of suits and ties for men and suits or skirts and blouse for women are appropriate.
Be aware of the heat and humidity in Indonesia - and ensure that clothes are lightweight and made of natural fabrics. If staying for a period of time, make sure to pack ample changes of clothes.
Evening functions can be more informal with short sleeves being worn by men and trousers by women. Only the most prestigious restaurants would expect a more formal approach.
Women should be aware of Muslim sensitivities and clothes should not be too revealing.