In my last several sessions I've noticed that my PC's are missing out on a lot of the details of the story (such as NPC motivations, optional pathways to objectives, etc.) by not asking the right questions or not receiving the right information about a situation.
Let's go with an example: The big baddie is an Inquisitor who was a former member of their team turned bad, who has a personal vendetta against the group because he believes that they killed his family. I as the GM know that his family was slaughtered by the Empire and holofilm was forged to make it look like the party, but the PC's don't. The only thing they know is that one time he shouted at them, "You killed my family!"
Now obviously I take blame here, as I'm not setting up the story right and delivering the information the PC's should have. So my question is this: How do you as the GM give out information, NPC motivations, and backstory of any element to the PC's without outright telling the PC's the information? Do your NPC's open up to the party forthright, or with a few checks? Do those checks determine exactly how much the PC's learn?
Thoughts?