Actual timeline of events-
1 - Diane at the dinner
While the movie timeline starts with Camilla/Rita's Mulholhand Drive sequence, the actual reality timeline starts with Dianes ride down Mulholland Drive, to dinner (even though its seen as a flashback.)
The characters there will later be incorporated into the paranoid fantasy of her dream:
The director talking about the pool man, becomes the director in her dream, also with Dianes idea of the pool man.
The fat man who who doesn't like his coffee becomes the gangster who doesn't like his espresso.
Coco, the director's mother, becomes her landlady.
The cowboy-hat guy becomes the cowboy-hat Hollywood power figure.
The girl who kisses Camilla becomes the "Camilla Rhodes" in the dream part.
And of course, Camilla, her ex-lover who becomes the dependent, loving person Diane wants her to be, "Rita".
2 - Diane at Winkies
After the humiliation at dinner, Diane decides to kill Camilla. At Winkies, we meet the hitman she hires. He remains the hitman (and becomes a pimp) in her dream, although an amusingly incompetent one.
The scary man in the background of this scene becomes the man with scary dreams in the dream-Winkies scene.
Dianes fear (acknowledging the reality of the murder) is projected into her dream as the mans fear, the scary bums face. We later see the connection, as it is this dream-bum who holds the box.
The single stack of dirty money is dreamed as clean, neat multiple stacks.
The plain blue key, that opens nothing but represents the murder, becomes futuristic looking, and now represents the 'key' to opening the repressed reality of the murder she is responsible for, hidden in the blue box.
The waitress at the diner becomes the prostitute.
The waitress's name, Betty, is the name Diane takes in her dream personae.