Other mistake: When the Falcon speeds away from Hoth just as Darth Vader steps out, watch carefully as the Falcon exits the hangar. You will notice that a very small spot of the Falcon is visible through the roof of the hangar as the Falcon exits and flies upwards.
Revealing mistake: After Luke escapes from the snow monster, he collapses, and there's a shot of Han riding. When the camera pans down, there are no tracks in the snow where the tauntaun just ran.
Continuity mistake: When Luke crash lands on Dagobah, the view through his cockpit is crystal clear. But when the canopy pops open, the glass is dark tinted.
Continuity mistake: Just after the Falcon leaves the hangar on Hoth, we see Luke watching the Falcon as it rises up into the sky. Look closely at Luke's head - he is looking at a point ahead of where the Falcon actually is.
Continuity mistake: Leia and Han become annoyed with C3PO's chattering, and Leia turns him off. However, if you watch him in the background, you can see his body move as he breathes.
Visible crew/equipment: In the Hoth sequence, after the asteroid hits near Luke, you can clearly see the boom mike in Luke's goggles on his forehead.
Continuity mistake: Widescreen version: In the shot where Luke's hand is cut off, two of the poles that Vader just cut through can be seen in the lower right hand corner. The poles are much closer together than in the rest of the scene.
Continuity mistake: When Luke is hanging upside down in the monster's cave he uses the Force to get his lightsaber. In the shot from Luke's POV it's about 3/4 buried in snow, but in the reverse it's only about 1/4 buried.
Continuity mistake: When the Millennium Falcon goes towards the bottom of Cloud City towards the end of the movie, we cut to the inside of the cockpit and Lando says "Look, someone's up there" when he notices Luke on the weather vane. At this point you can see Lando's right hand is on Chewbacca's seat when he says this, but when the camera is behind Lando in the next shot, his right hand is no longer on the seat.
Continuity mistake: When Han says "Watch this!" when trying to get the Millennium Falcon to jump into hyperspace, C3PO turns his head around twice.