While I'm a huge fan of Star Wars and have read many a book to gain lore, I feel like I don't have a good grasp on what's going on in the galaxy at large between ANH and ESB. For instance, I know that the Mon Calamari join the rebellion, but have no idea how that works. (i.e. why didn't the Empire send a fleet of ISDs to subjugate a planet in open rebellion?)
Another example: from searching Wookieepedia, I came across the blockade around the Gordian Reach (Yavin IV) that apparently went on for six months ABY. Based on that, I'm looking at a blockade-running mission, which my crew may start not knowing they're working for the Rebels.
I realize I could just make stuff up, but I've found I'm much better riffing off a bit of lore than coming up with something from scratch. Any suggestions on major bits of history like that would be greatly appreciated.