Characters and situations should be driven by the needs of the story, not the desire to create as many toy options as possible.

Every character needs their moment in the spotlight. That thing that only they can do to help everyone else out/push the story along. Even ROTJ mostly got this right. This goes hand in hand with don't bring back a character for a glorified cameo if they have no impact on the plot.

Don't take us where we've already been unless there's a damn good reason to go back there. Tatooine has been done to death.

Keep light saber battles realistic, this isn't The Matrix.

Star Wars needs to be fun again. (A word George himself once used to describe the original film.) That doesn't mean it can't be dark in places, but people need to come out of the theater exhilarated and happy, and itching to see it again.