When I'm learning Indonesian, I see that there are several ways of saying "you" or "I". What are all the different ways to say the personal pronouns and what differentiates them from the rest? Does it have to do with grammar, or can you put whichever one and make it mean the same thing? Thanks
The default for you is anda (polite) or kamu (intimate). The default for I is saya (polite) or aku (intimate). Others than those are dialetical pronouns from each area.
Use saya/anda (usually you would switch from 2nd pronoun to 3rd polite pronoun instead though, like "Bagaimana dengan bapak?" = "How about you, sir?") for talking to elders, to respected persons, to important persons, or in formal occasion, and aku/kamu for talking to someone younger than you, someone with the same age as you, or in informal occasion.
For me, the rule of thumb is use saya/anda (or 3rd polite pronoun) until you know which pronouns they prefer to use.