Often it's not clear what an NPC's motivations are - whether the NPC will help or hinder the PCs. So it pays to be circumspect until you find out what their intentions are. The problem with this is that you don't want to give information to potential enemies, when at the same time you might need to give that information to potential allies.

This is where Detect Evil and similar spells and magic items come in handy. In games without magic, you have to make do with some other approach. Some methods make use of skills like Bluff, Diplomacy, Empathy, Psychology, and so on. You might even roleplay a conversation in detail.

But generally it's easier and more effective to just say whatever you feel like and mop up any damage later.

Transcript

Tion Medon: What brings you to my world, Master Jedi?
Obi-Wan: Hmm. I don't know if I can trust this guy. I use the Force to sense his emotions.
GM: You sense pride and strength, tempered by sadness and resignation.
Obi-Wan: I pursue... a fugitive from justice.
Tion Medon: A Jedi on the hunt. I would not like to be the hunted.
Obi-Wan: I seek only those responsible for the kidnapping of the Chancellor.
Tion Medon: We mind our own affairs on Utapau.
Tion Medon: {to workers behind him} Hey! Refuel this Jedi's ship.
[SFX]: Step {Tion Medon steps up close to Obi-Wan}
Tion Medon: The Trade Federation army is here. My people are besieged.
Tion Medon: You may take what you wish from their remains when we have overthrown their cabal.
Obi-Wan: You realise they are the most dangerous organisation in the Galaxy?
Tion Medon: Though it take a thousand years, we shall reclaim our planet. Until then we marshal our strength.
Obi-Wan: Oh. You don't think you could hurry it up a little?