The character "Q" records a demo of his scratching routine in his bedroom. When he goes to the audition and his tape is played it is different from the version he recorded in his room. It is a bit longer and the scratches are more complex.
After the scene in which Q, Bishop, Steele and Raheem had the altercation with Radames and his crew, they ran around the corner and Bishop lit up a cigarette and the very next shot, he has no cigarette and his hands are in his pockets. Then he takes a drag off Raheem's cigarette.
When Q is looking through the New York post newspaper he is reading about Raheem's murder and you can see the date of paper which was Tuesday is April 16th 1991. Then you can see some of the article about the murder and in the paper it says it happen on April 8th which would have been a Monday however Q and his crew robbed the store on a Saturday so the date should of been April 6th.
When Bishop and "Q" are on the ground of the roof in the final fight scene, you can briefly see a foot of somebody else in the corner of the screen even though they are supposed to be alone on the rooftop.