During the first party sequence Monty walks in and greets Serena, who is in the black chair. The camera cuts and pans over and Serena is sitting on the end of the couch farthest away from the black chair.
During the first shot of the end party sequence, Monty walks out and offers Calvin a beer, walks over to the bar and begins talking to Serena, You can see the High School girls in the background. Cut to close-up of high school girls, enter Serena from the right, follow her left and there is Monty standing at the end of the line.
Towards the beginning of the movie Monty comes through the main entrance of the restaurant he is wearing Converse All Stars, a few minutes later he is wearing black dress shoes then later Converse again.
When Dean is bringing cocktails to the Jack's Steakhouse owner's table, he serves cocktails to the two people on Jack's right. The camera instantly cuts to Jack, who raises his hand with a full cocktail in it.