It's important for NPCs to have their own motivations and goals. And not just enemies - allies are equally important. They shouldn't simply be puppets of the PCs and go along with whatever they want. So try giving them a scene or two to establish their identity, their role in the world, and their plans for the future.

And if things get in the way of those plans, that gives you seeds for recruiting the PCs into adventures aimed at setting things right again.

Transcript

Bail Organa: Captain Antilles?
Captain Antilles: Yes, sir?
Bail Organa: I woke up this morning, you know... and the sun was shining, and it was nice, and all that type of stuff.
Captain Antilles: Sir?
Bail Organa: Now the Jedi are gone, the Republic's in a mess... It's tearing me apart!
Captain Antilles: Sir??
Bail Organa: Keep these droids safe until Obi-Wan returns. Then we're gonna do some cleaning up around here.
Captain Antilles: Here? But the ship is spotless and gleaming white.
Bail Organa: I mean around the Galaxy.
Captain Antilles: Sir?
Bail Organa: We know what needs to be done now. Take down the Man.
Bail Organa: Our Rebellion has a cause.