Indonesian splits this territory differently from English, and the mistakes are predictable.
Maaf is the apology
Maaf, saya terlambat. ‘Sorry, I’m late.’
Maaf, boleh tanya? ‘Excuse me, may I ask something?’
It works both as a real apology and as the opener to a stranger, exactly like the English “sorry” in “sorry, do you know where…”.
The reply is tidak apa-apa ‘it’s nothing’, or nggak apa-apa in speech, often shortened further to nggak apa.
Permisi is the one you will underuse
Permisi. ‘Excuse me.’
You say it when you walk past someone seated, when you enter a room, when you leave a group, when you squeeze past in a shop. Indonesians say it many times a day, in situations where an English speaker would say nothing at all and simply move.
This is the single easiest way to sound less foreign, and it costs you one word. Not saying it is not rude exactly, but saying it is noticed and appreciated.
Tolong and silakan both mean please
They point in opposite directions, and this is where people get caught.
Tolong is for asking someone to do something. It literally means help.
Tolong tutup pintunya. ‘Please close the door.’
Tolong ulangi. ‘Please say that again.’
Silakan is for offering or inviting.
Silakan duduk. ‘Please sit down.’
Silakan masuk. ‘Please come in.’
Using tolong when you meant silakan turns an invitation into an instruction. Saying tolong duduk to a guest is closer to “sit down” than to “do have a seat”.
The test: if you want something done for you, tolong. If you are giving someone permission or inviting them, silakan.
What you’ll actually hear
What the book says: Tolong berikan saya air.
What you’ll hear: Minta air, ya.
Minta ‘to ask for’ plus ya at the end is the everyday way to request something, and it is softer than it looks written down. Tolong is kept for things that are genuinely a favour.