Dyeing for Your Art: Linda Hamilton is a much more physical presence in this movie than in the previous film.
Enforced Method Acting: When Sarah is bludgeoning the nurse who assaulted her with a broomstick, that's Linda Hamilton really whacking the actor. Apparently, he was pretty hesitant to hit Hamilton with a nightstick in a prior scene, which caused a lot of takes of a physically demanding sequence for Hamilton (one that didn't even make the theatrical cut), and she took out some frustration in return.
The T-800 inexplicably saying "I need a vacation...", but James Cameron found it so funny he left it in.
In addition, Sarah Connor knocking out the orderly with a broom, as well as the resulting injury, was indeed real. She, or rather, the actress, did it out of revenge because in an earlier scene the orderly went a bit too easy on her during the acting. They kept it in for the final cut (no pun intended).
When Cameron first told Arnold about a sequel in 1985, he said it would feature two T-800s, one of which would become a metal skeleton. When he actually begun working on the second one in 1990, he decided to turn the evil Terminator into the T-1000 instead.
WASP singer Blackie Lawless was considered for the role of T-1000.
Shaquille O'Neal reportedly asked for a role as a black Terminator.
Michael Biehn was originally supposed to be the T-1000, but the studio thought this would be too confusing.
Earlier drafts of the script included many scenes that was ultimately left out in the final script:
Alternate beginning has an extended battle sequence of the future war, with John Connor as the narrator, who mentions Judgement Day happened in 1999. It also describes many different war machines besides the flying and tank H/Ks. It shows the machines shut down, since Skynet has been defeated. It shows the soldiers breaking into the Skynet complex and sending Kyle Reese into the past. The sequence ends with John Connor looking at a storage area holding the Terminators with human skin, he finds a row with identical appearances (the Arnold model), and looks at an empty case (of the Terminator from the first movie) and the Terminator next to it. Then we flashback to Janelle trying to call John in the garage.
A scene which Sarah was forced into shock therapy. She flashback to when she crushed the Terminator in the first film. Then we cut to the scene of the second Terminator's arrival.
Sarah's alternate dream after she was forced into taking the pills. After chasing after Reese, she was ambushed by the orderlies, then the Terminator came and grabbed her, and took her outside, to the playground. The nuclear explosion struck and it ends with the shockwave blasting the skin out of Sarah and the Terminator.
The Gant Camp sequence. A more extended and alternate version of the Salceda Ranch sequence. Travis Gant was the "ex-Beret guy" John mentioned in the film. Here Gant is married to Yolanda while Salceda is instead one of Gant's men. They all find out that Sarah was telling the truth about the Terminators. After John and the Terminator chase after Sarah, the T-1000 came and killed everyone at the ranch. There's also a scene where the T-1000 was listening to a recorded message from Sarah telling John to go to Gant Ranch; right before he heads there, a couple of cops came to arrest him when they discover he's driving a stolen police car, then we cut to the T-1000 in the motorcycle.
Similarly, there's a scene which the T-1000 arrives at Salceda Camp and kills him, but lets his family live after he kindly asked them where John is.
Sarah's second dream sequence instead has nuclear missiles coming from beneath the playground, and the blast from the ignition incinerated the people and Sarah.
Linda Hamilton apparently forgot her earplugs for the scene where the T-1000 attacks Sarah, John and the T-800 in an elevator and incurred permanent hearing damage from all the gunshots fired in an enclosed space.
Schwarzenegger commented during an interview that doing the one-handed shotgun flip-cock nearly broke his fingers when he accidentally flip-cocked the unmodified gun instead of the prop gun specially modified to be flip-cocked in that shot.
The biker bar scene was filmed across the street from where the Rodney King incident occurred, and was also filmed the night of the beating.
The biker bar set was apparently so realistic that a female passerby walked in (having missed the camera trucks and film equipment), mistaking it for a real bar. When she saw Arnold Schwarzenegger wearing colourful shorts, she asked what was going on. Schwarzenegger replied that it was male stripper night. Hilarious in Hindsight considering where the T-800 got his clothes in the sequel...
The scene where the T-1000 disguises itself as Sarah to try and kill John? That's not special effects, that's Linda Hamilton's identical twin sister Leslie playing Sarah's doppelganger.
And the scene where the T-1000 assumes the appearance of Lewis, the guard, then kills him? That's also not special effects; that's the work of having Don Stanton play Lewis while his identical twin brother Dan plays the T-1000.