Food on board can be a bit basic -but you can get something at every airport - eating is national pastime
Check with the airlines that they take credit cards - also you may have to go to the office in town to make changes to your tickets
However poor you are you are a damn sight richer than most Indonesians and as a matter of course you will be expected to pay/tip accordingly - not a lot in real terms but any decent Guide Book will steer you correctly
Only pass money with your RIGHT hand, NEVER shout or point - a vague wave is allowed. Do NOT touch anyone (even kids) on the head. Expect very intrusive questions on any aspect of your life from any casual passer-by - it's not an insult - they're genuinly interested in you
Smile all the time - everyone loves a stupid foreigner
GO WITH THE FLOW - there are 200 million of them and there's you - you can swim across the current but it's not restfull or effective - things amazingly do get done - just not necessarily the way you expect