Rainwear is essential. It is based on Tagalog but contains elements of some other Philippine languages. Spanish is still spoken by some, particulary the upper classes. There are 100 cultural and racial groups in the Philippines, all of which have their own language. The Philippines is, in fact, the only Christian country in Asia.
Casual dress is acceptable in most areas but, in Muslim enclaves, it is best to cover up.
Women in particular should not wear anything revealing. Many Filipino men will, on formal occasions, wear an embroidered long sleeved shirt or a plain white barong tagalog with black trousers. The Philippines are probably more Westernised than any other Asian country. There are many ethnic minorities in the Philippines - the Ifugao, Bontoc, Kalinga, Palawanun in Palawan, and Ilokano in North Luzon, the Negrito in Central Luzon, and so on. If visiting these areas it is advisable to acquaint yourself of local customs and traditions so as not to inadvertently offend.