Lets say your group of players has a destination set by the mission they are on. Thing is, they can pick any number of routes and interact with a wide variety of systems in between.
Would you make your players decide their route first, perhaps at the end of a session, so you can at least familiarize yourself with the worlds they may visit,
or do you just try to wing it, perhaps having Wookieepedia open and do the best you can to improvise should they choose to stop and enjoy the locals along the way?