Desmond wrote:SAYA and AKU
Saya can be used either in formal or informal situation. It's considered more polite than aku in general. You willl always make yourself sound natural and polite if you use saya whether you are in formal or informal situation.
Aku is used in a less formal situation. It's used among friends (besides GUE or GUA) and I see that it's more commonly spoken among teenagers.
In informal situation, it's also a personal preference to use saya or aku. I myself never use aku. I hate it.
I prefer gue or gua when talking to friends.
In accordance with what Desmond states about aku, the word seems to have been growing obsolete in the spoken language in Jakarta. It hasn't disappeared at all, but is being used less and less, with people, especially young people, preferring guè/gua in the spoken language.
As for saya, its situation is quite stable and is relatively the "safest" word to use as the 1st person singular pronoun (guè/gua and aku are used only in informal situations).
Note that saya can mean I, me, and my
Nama saya Pauro
= My name is Pauro
Saya orang Polandia
= I'm Polish
Ini untuk saya?
= Is this for me?
The same goes for guè or gua.