The safest assumption you can make about anything unknown that you see in a roleplaying game is that it's an enemy and you should kill it. Let's face it, 95% of the stuff you meet is out to kill you, so this is actually a pretty good working approximation.
It saves you all the hassle of trying to figure out if it's going to rip your face off or not before it tries to rip your face off.
And the rare occasion that you're wrong? That's what clerics are for! (Or post-mortem brain-scans, if you're not playing a fantasy game.)
GM: A clone trooper transport picked up Padmé in the desert and delivers her to the landing platform.
GM: You arrive just in time to see a ship taking off.
Padmé: I shoot it down!
Clone Trooper: How do you know it's even a bad guy?
Padmé: Who else would be fleeing from me?
R2-D2: Let's see... Governor Bibble...
Padmé: Bubble's in there?! I fire wildly!
GM: Your blaster is too weak to penetrate the armour.
Padmé: After it!
Clone Trooper: It's a spaceship. This is a hover transport—
Padmé: Modify the engines or something!
Clone Trooper: —with no walls.
Padmé: Hold your breaths!
R2-D2: When's he going to realise Bibble isn't a bad guy?
Clone Trooper: I'm not holding my breath.