After Djay buys the keyboard from the bum at the beginning, he holds a paper bag in his right hand and the keyboard in his left. When he goes to play the keyboard, the bag is gone.
When Djay first plays his keyboard, the dirt pattern on the door behind him changes drastically when the scene changes.
When Djay records "It's Hard out here for a Pimp," Nola's hands jump to her headphones between shots.
When Djay lays down the track for his song, his hair is slicked back in the recording studio, messy when he is told to go outside, then slicked back again when he returns to the studio.
When Djay and Nola are in the car in the opening scene, the view of the john from their back window shows the window rolled down 10-12 inches. A moment later, when Nola exits the car to get into the john's car, the same window is open about 1 inch.
At the beginning when DJ turns on the radio, the music being played is explicit and uncensored. If it was being played on the radio, it would be censored to make it radio-friendly.
Clyde buys batteries for his microphones. They turn out to be Shure studio microphones that don't use batteries. Studio mics rarely use batteries. He could have been buying them for microphones used in his other endeavors, such as wireless microphones or the deposition microphones that appear later in the film.
Toward the end of the scene in which Djay is arrested, the padding used to make Shug appear pregnant is visible.
When Djay changes the radio station in the car, the FM analog tuner is visibly set to the left side of the dial close to 94, but the announcer identifies the station as 107.
When Shelby lays down the piano loop for "Whoop that Trick", he plays it in the middle of the keyboard. In the next shot, his hand has moved to the bottom of the keyboard, while the notes stay the same.