Passport with at least 6 months validity;
2 photocopies of your passport: we need one for port clearance, and you should keep another one just in case;
A print of your return ticket to Indonesia (sometimes Indonesian customs officers ask for it to let you in);
Photocopy of your insurance policy with the necessary information to make a claim (contacts, procedures, etc.);
Credit/debit card to take cash from ATM machines;