In the first Barbershop, the tattoo of the woman is on Ricky's left arm. In the sequel, it appears on his right arm. This may not be evident because he is wearing mostly long-sleeved shirts in the first movie, but one of the deleted scenes shows him in a tank-top and the tattoo is visible.
When the first ever sign went up announcing the rival "Nappy Cutz" franchise, Calvin and the others run across the street to look at the sign. A long shot of them reveals a brand new coffee shop behind them. Later in the film, we see the coffee shop in the process of just being built.
When Alderman Brown and the TV crew enter Calvin's barbershop, the red 'tally' light on the front of the camera is flashing, so is the warning light on the rear left. Flashing red indicates either a low battery, slack tape or internal humidity. It can also mean 'running up to speed' but any cameraman worth his weight would already be turning over BEFORE he enters the shop, not during.
In one scene, Isaac pulls up the "Nappy Cutz" website on his Mac laptop to show the rest of the barbershop. However, the active application seen in the insert shots is plainly seen to be "DVD Player", not a web browser, revealing that the video clips supposed from the website are being run from a DVD disc or local file.