When Renton and Spud are in the restaurant to share a soda with 2 straws, once they finish there's one straw sticking out towards Renton, but as the camera moves between shots of them the straw is either pointed at Spud or is gone altogether.
When Begbie throws the beer glass behind him over the the balcony, it has less than a quarter of beer still left in the glass. Then after the cut-scene with Tommy telling the truth about the Pool Table incident, the scene continues & is then immediately followed by another shot with an empty, & dry looking beer glass. It isn't even wet looking, let alone spilling the small amount of beer that was previously left in the glass when Begbie chucked it over.
When Renton is in his bedroom being forced off heroin by his parents and the baby is crawling across the roof towards him after Sickboy has made an appearance, there is a close-up shot of Renton cowering against the pillow. The shadow of the camera is visible against his face and the pillow.
When Diane meets Spud lying comatose on the street, a bus passes by in the background. The bus is orange, which is the colour of Glasgow City buses, but the movie is set in Edinburgh where the buses are maroon and cream.
About 41 minutes in, when Spud and Renton are running down the street, several passers by stop to look at the camera, most notably the two women at the left of the screen and the two men carrying bags near the corner from which they have run.
When Tommy wants to try heroin and presents the folded banknote to Renton (seen from both Renton's and Tommy's point of view), the imagery partly visible on one side of the folded note is not consistent with that on the other side.