1. The version of Rey in Michael Arndt's early scripts was called Kira, and she was described as a "loner, hothead, gear-head badass."
2. Unlike Rey, who is extremely reluctant to leave Jakku, Kira was eager to leave the planet, and a scene was written in which she fantasizes about leaving while watching spaceships arriving and departing from the planet.
3. The version of Finn in Arndt's version was named Sam, and all early art depicted him as a white man. Sam was described in Arndt's scripts as "pure charisma."
4. The earliest version of Poe Dameron was tentatively referred to as John Doe, and production art depicted him as a black man. The character's role in the film varied a lot — he was briefly considered as a Jedi, and then as a bounty hunter, before they landed on making him a pilot for the Resistance.
5. When Poe was written as a bounty hunter, he had his own Wookiee sidekick.
6. Poe Dameron was originally going to die in the crash landing on Jakku, but J.J. Abrams decided to write the character into the second half of the movie.
7. BB-8, known simply as "Surly" in early production designs, was originally written to first appear in a droid repair area on a Star Destroyer. Droids that could not be repaired there would simply be tossed into a furnace.
8. Finn's defection from the First Order was originally written to come after witnessing the airlock ejection of a captured Resistance crew.
9. A version of the script had Finn being rescued by an indigenous tribe after crashing the TIE fighter on Jakku. The tribe would've performed a healing ritual on Finn, signaling his rebirth as a hero.
10. The now iconic image of Kylo Ren stumbling through the forest on the Starkiller Base and igniting his lightsaber from the trailers was cut from the final version of the movie because it didn't fit well into the film. "There might be a look or scene in a trailer that identifies as being powerful in that short form, but sometimes that doesn't jibe with what's happening in the long form," J.J. Abrams told the Associated Press. "There were a couple of shots that ended up not being used in the film, simply because we were doing our best to make the movie be the best version of itself, which sometimes means losing a moment here or there."
11. The primary antagonist of the early drafts was tentatively called the Jedi Killer, and the character's appearance went through many Vader-esque revisions.
12. One of the many designs for the Jedi Killer was reworked as the design for the Guavian Death Gang enforcers who raid Han Solo's freighter.
13. One version of the Jedi Killer was sustained by sun matter, and you would see him in his meditation chamber grasping and eating sun energy in the room.
14. For a time, the Jedi Killer was to be accompanied by a floating torture droid that resembled a cross between the interrogation droid used on the Death Star in A New Hope and the Imperial probe droid seen at the beginning of The Empire Strikes Back.
15. Jakku was initially conceived as a massive, planet-sized junkyard with design elements inspired by 1960s spaghetti Westerns and the 2011 Afghani short film Buzkashi Boys. The now iconic images of the crashed Star Destroyer and fallen AT-AT were around from the beginning.
16. A downed Star Destroyer was also incorporated into the design of a lush green planet where Leia was going to be introduced, but that planet was cut, and the idea to have two crashed Star Destroyers in the movie was considered too confusing.
17. Starkiller Base was originally meant to be on Dantooine, the planet Princess Leia tries to get Grand Moff Tarkin to destroy with the Death Star rather than her home planet of Alderaan in A New Hope. The First Order would have retrofitted an old Rebel base for their purposes.
18. General Leia's base was conceived as a hidden fortress, inspired by The Guns of Navarone, in the cliff walls at the Cliffs of Moher in Ireland.
19. Co-production designer Rick Carter briefly considered introducing a double-sided lightsaber, with one side having a blue blade and the other side with a red blade.
20. Luke Skywalker was more prominent in Michael Arndt's early version of the story, with Rey meeting him in the second act rather than Han Solo. This idea was scrapped because it upstaged Rey as the movie's lead. "It just felt like every time Luke came in and entered the movie, he just took it over," Arndt told Entertainment Weekly. "Suddenly you didn't care about your main character anymore because, 'Oh, Luke Skywalker's here. I want to see what he's going to do.'"
21. An early Rey-and-Luke version of the plot was focused on a search for the remains of Darth Vader.
22. Another version of the plot had Rey and Luke searching for some key bit of information about Jedi history hidden in the underwater wreckage of the second Death Star.
23. Yet another variation of this plot had Rey finding a hidden map inside the Emperor's tower in the submerged remains of the second Death Star, and that map showing where the Jedi are and where Luke is hiding.
24. A later discarded version of the plot revolved around a search for Luke's old lightsaber, and the first shot of the movie after the opening crawl would've been the lightsaber floating through space. Poe Dameron would've obtained the weapon from Lor San Tekka in the opening scene rather than the section of the map that would be hidden inside BB-8.
25. Darth Vader's melted helmet was also the plot's MacGuffin for a time, but was ultimately made an artifact owned by Kylo Ren without any explanation.
26. A dreamlike scene of Luke submerged in sand was conceived and illustrated, but abandoned. "The sand is pouring in on top of him, and he doesn't care," production designer Iain McCaig said, describing the scene. "At one point, he suddenly just opens his eyes."
27. McCaig also pushed for Darth Vader's ghost to appear in the film, and the image of the ghost would shift back and forth between Anakin Skywalker and Darth Vader.
28. The octopus-like Rathtar creatures were originally meant to be on the surface of the planet outside Maz Kanata's castle, but when that scene was cut, J.J. Abrams ended up putting them on Han Solo's freighter because he liked their design.
29. Maz Kanata was originally going to bring Luke's lightsaber from her castle to General Leia at the Resistance base. This scene was actually shot, and you can see a moment of the lightsaber being handed to Leia in the second trailer for the film. "It ended up being an unnecessary hot potato," Abrams told the Associated Press. "It felt like the movie was stronger if we skipped over that moment. It definitely wasn't meant to be diversionary. It was a scene in the movie I later realized I had put the entire crew through shooting, only to cut it."
30. The movie was also going to include more scenes with Leia, who was originally meant to be introduced earlier in the film, and her scenes would've focused on gathering intelligence from around the galaxy and plans to use a Resistance super-weapon.
31. The super-weapon was called the War-Hammer, and was designed as a massive ship with a huge front that could penetrate a shield and deploy ships through it. The War-Hammer would be several times the size of a Star Destroyer.
32. Supreme Leader Snoke was a female character at one point, and was later designed to look like a beautiful but warped marble sculpture.
33. Captain Phasma was originally written to be a man, but J.J. Abrams decided late in the casting process to flip the character's gender after realizing they could use a few more female leads.
34. A four-person TIE fighter and a red Star Destroyer were both designed, but ultimately not used.
35. A scene with several aliens gathering around a droid cockfight was considered for the sequence in the bar at Maz Kanata's castle.
36. A scene in which Maz Kanata asks Rey who she is and replies "no one" was cut despite being prominently featured in the trailer.
Unless otherwise noted, all information in this post is sourced from The Art of Star Wars: The Force Awakens by Phil Szostak, published by Abrams Books.