First, I'll come clean. I'm a Star Wars junkie. I've read and collected virtually all the novels, and some of the Dark Horse comics stuff. I've got the Star Wars films in three different formats. I've been collecting the Clone Wars series on Blu Ray as it has been coming out. I bought the 3 volume Star Wars Encyclopedia at a store closing sale from Borders a few months ago. So I've got a stronger sense of Star Wars canon than any player I've ever had.
Still, I could care less about the continuity of any of that when I'm running a Star Wars RPG session. I see so many GMs who walk on eggs in fear of whether players will be upset with them for messing up canon, or worst still, GMs destroying their own game because they are afraid of destroying canon that I've got to say, take canon, put it in front of the Death Star's laser, and fire the laser on full power.
There are some things players of ANY RPG based on a licensed property, or even just an extensively published original RPG setting (cough. cough. Greyhawk. Eberron. Forgotten Realms. cough. cough.) need to understand if they really want to get the best out of their games.
1. YOUR PLAYERS' CHARACTERS SHOULD BE THE STARS OF THEIR STORY.
I'll come clean. I hate playing or running in the canonical Rebellion Era. What makes for a great pulp-space cinematic story in the Original Trilogy (a handful of determined, talented, doggedly loyal to each other friends taking down a Galactic Empire) makes for a terrible RPG setting. A canonical Rebellion Era dooms the PCs to being a B plot. Think about it. Luke destroys Death Star I. Luke becomes the first (and only during the Original Trilogy) new Jedi. Han and Leia lead a group of rebel troopers (and Ewoks) to destroy the shield generator on Endor. Lando and Wedge destroy Death Star II.
None of those characters are PCs. So what do your players get to do? Maybe they get to be Rebel Trooper #111 on Endor. Maybe they are Rebel Pilot 26 in a snowspeeder trying to delay the Imperial invasion of Hoth. Then again, maybe their actions are off-screen entirely. The one time I ran a canonical Rebellion era game, the climax had the players lead a diversionary action elsewhere while Luke, Han, Lando, Leia, Wedge, R2D2, C3PO, Chewbacca, et al. were destroying a Death Star. B plot. Strictly B plot. It was easily the least satisfying campaign I ever ran.
To make your game more satisfying, play fast and loose with canon. Lucasfilm certainly has over the years (mitichlorians, Leia knew then couldn't have known her mother, retconning Obi Wan's knowledge of Luke's father being Vader, various Expanded Universe gaffes). Feel free to have Wedge catch a case of food poisoning the day of the Death Star battle over Endor so a PC can have a chance to save the world. What does it matter? It's not like somebody is going to reshoot Episode VI to make it match what happens in your game.
2. NEVER LET YOUR PLAYERS KNOW WHAT IS COMING.
The other big problem with canon, particularly with a canon heavily developed along a timeline with an overarching metaplot (Star Wars, Dresden Files, Star Trek, anything publishing using the Cortex System) is that the players have a good sense of what is coming. In Star Wars, we even name the various eras in the timeline, and each of them has a very different feel (Rebellion Era, Prequel Era, Dark Times, Old Republic Era, New Jedi Order, etc.).
Even though players may not know the details of your campaign, they do have a pretty good sense of the general feel of the era, particularly if the game adheres to canon. For example, in a Dark Times game, your players go in knowing the Emperor has been triumphant, the Jedi are gone, force-users everywhere are hunted, repression is everywhere (particularly for non-humans), and eventually the seeds of a rebellion will coalesce.
Feel free to mess with the feel of the eras. Let ideas and concepts from other eras bleed into the era you've set their game in at least a bit.
An example of this is the campaign I'm running right now. It's set in the Prequel Era (moving towards the Clone Wars era, but between the first two films). The party is centered around a young Jedi Padawan who becomes a Knight, a young noblewoman who is a distant cousin of Padme Amidala, and a wise cracking Dug pilot/mechanic. In the early stages, younger Jedi just keep disappearing without a trace. The players are employed by Supreme Chancellor Palpatine, and so far he's been more than accommodating to every request made, interfering little with their missions once assigned.
Now, the players are beginning to run into all sorts of red lightsaber wielding dark siders? Are they Sith apprentices? Or are they Dark Jedi who defected from the order as part of the disappearing Jedi and stumbled across the wrong sort of knowledge? Is the Rule of Two still operative? Is Chancellor Palpatine really the one-dimensional villain he is made out to be in the movies?
Even though outwardly, the campaign looks an awful lot like the Republic from the Prequel Era, there are just enough oddities to create a sense of cognitive dissonance...a sense that maybe things aren't quite what they seem to be on the surface. Even if running a campaign in an era with a well-established canon and generally planning to adhere to that canon, I encourage GMs to create this sense of not knowing for sure how things are going to work out. Make the tactics of some members of the Rebellion morally questionable from time to time. Let your players run into honorable Imperial officers and soldiers. Create that sense of verisimilitude by changing things up a bit.
3. THE CARE, FEEDING, AND KILLING OF CANONICAL CHARACTERS
There's an unwritten rule that I've always adhered to when designing or running campaigns. Never put an NPC into the game if you aren't prepared to have them killed the first time the players meet them.
A classic example of this was when I ran the WotC campaign for Star Wars Saga Edition, Dawn of Defiance. It's a pretty solid series of linked adventures set during the Dark Times Era. Without giving too much away, the true Big Bad Evil Guy of the campaign is a recurring villain. By the end of the adventure, everything imaginable happens to this character. In the final battle, he basically winds up looking like Darth Vader without the really cool black helmet he's been wounded so much he's lost so many limbs and organs.
That's, of course, if the characters don't kill him outright the first time they encountered him by blowing a boatload of Force Points and Destiny Points. Which happened. In my game. My players were rolling exceptionally well, I rolled exceptionally poorly, and before I knew it, the recurring villain was being skewered on the business end of a lightsaber. Ouch. The campaign pretty much died with him.
My point is that in an RPG, no character should be more precious or sacred than any other, particularly NPCs. It's a slight spoiler here, but a decade old, so I'm going to give it away. Chewbacca's death in Vector Prime (New Jedi Order series of novels) was handled ridiculously by the fans. The unfortunate author, R A Salvatore, received death threats...yeah, that's right, real death threats because he killed off a fictional character in a novel.
Once you got through dealing with the shock though, the story made sense, both from a literary point of view (how do you write a character that doesn't speak in a recognizable language?), and from a dramatic point of view (nothing says "shit just got real" quite like the death of a beloved character). To me, it was written well (he dies saving others), and served to let people know in a way that every previous Star Wars novel had failed to, that the galaxy was dangerous, that the antagonists were utterly ruthless, and that all of a sudden you feared for the rest of the heroes of the story. Whatever you may think of the New Jedi Order series of novels (and opinions are decidedly mixed), that moment, to me, was one of the most dramatic moments of the novels. Mission accomplished.
In the most recent session of my campaign, I killed Padme Amidala. It happened off screen, so the characters learned about it by being contacted by the Chancellor's Office. As a character, she no longer served a story function, she was in the way of making one of my characters the star of the story (See Rule 1 above), and it just felt like the right time. My wife, who plays her cousin, a noble diplomat, actually teared up a bit upon hearing the news (I basically rewrote things to let the bomb on the landing pad seen at the beginning of Episode II actually kill her and the rest of her delegation). Her death served a dramatic function, it increased the sense of danger, and even advanced the campaign's metaplot. The handling of the news, the roleplaying that came out of it, and the story that will come out of it took to the game to a level I've rarely ever achieved running a game, and have never seen playing in a game.
4. PUTTING IT ALL TOGETHER
All of this thinking led me to my current campaign, which has been entitled Anakin Takes a Bullet. To understand the thinking behind the campaign, I'm inclined to believe in a blend of the Great Man Theory, combined with a more social evolutionary approach.
To put this in Star Wars terms, Anakin Skywalker and the Emperor were the men, more than any others, who helped to bring down the Republic, but the state of the late Republic (endemic government corruption, rising internal disorder, economic decline, political conflict between the Outer and Inner Worlds, ossification of the Jedi Order) created the conditions under which they were able to destroy it.
I envisioned a multi-generational campaign, where the players would take a few sets of characters through the events of the Rise of the Empire, through the Dark Times, the Rebellion Era, and at least in to the early stages of the New Republic.
My first, and foremost goal was Rule 1, making the players the stars of the story. If you want to make the players the stars of the story during the time period covered by the six films, one of the easiest ways to do this is to remove the A plot, that being the Skywalkers story. How do you do this? The simplest way is to kill the Skywalkers.
In Episode I, during the podrace, there are several scenes in which we see Tusken Raiders, on one part of the course, taking potshots at racers using a slugthrower rifle. In one scene, we see Anakin's racer get grazed by a bullet. This is the point of divergence.
In Anakin Takes a Bullet, this shot instead hits Anakin in the brain. Even if he had a chance to survive the gunshot wound, The resulting trauma injury from the crash of the podracer finishes him. And in a stroke, no Anakin, no Luke, no Leia.
With ObiWan, QuiGon, and Padme now trapped on Tatooine (their ship now the property of Watto), Darth Maul can now deal with them at his leisure. Instead of the lightsaber battle on Naboo, the Sith Lord confronts the Jedi on the streets of Mos Espa. To create this battle, I actually statted up Episode I era versions of the three characters and let them duel it out. Ironically, as happened in the film, Qui Gon dies, but weakens Darth Maul enough that young Obi Wan, with the profligate expenditure of Destiny Points, kills Darth Maul in turn.
Enter the players. Their job is to pick up the paces of the failed mission on Tatooine. After retrieving Padme, Obi Wan, the rest of the group, and the body of Qui Gon Jinn, the group returns to Naboo, and the rest of the story from Episode I (alliance with the Gungans, battle with the Trade Federation Droid Army, destruction of the Droid Control Ship (with one of the PCs firing the shot that destroys it) proceeds from there.
But with this one death, Anakin's, a thousand ripples have spread. The Jedi must keep searching for their Chosen One. The PC Jedi becomes newly promoted Jedi Knight Obi Wan's apprentice instead of Anakin. The PC Noblewoman gets promoted from Handmaiden to diplomat for the Queen of Naboo, Padme. The Chancellor will need to find a new fallen Jedi through which to engineer the fall of the Republic, and other concerns are beginning to crop up. All because of one bullet.
DISCUSSION, DISCUSSION, DISCUSSION
One of the biggest challenges of a game like Star Wars or any other game with an extensively developed setting is selling your players on variations on a theme. I've been very fortunate in that my main RPG group, my family, have played together long enough, that we've developed a rapport, and they know, regardless of how experimental I get, that their characters will be treated fairly, that their characters will experience interesting stories and situations, and that together we'll make it a good game.
For those less fortunate, I encourage you to talk with your players. Seek their views on canon. See if they would be open to such a game. Emphasize that the changes you make are intended to give their players the opportunities to be the stars of the show, rather than a sidekick. And most of all, never let canon get in the way of a good game.