My dad is hosting (and cooking) a seven-course Italian dinner for 20 people on Saturday. My Mom and I are going to be the “waitresses.” Any ideas on what sort of outfits we should wear? Thanks!
I’d go with a tux. And a long white apron.
This is what I had to wear when I was a waitress at an Italian restaurant in the Bloomfield section of Pittsburgh:
White tuxedo shirt (available at uniform store)
Black bow tie.
Black knee-length skirt.
Black hose.
Black half-apron.
Black shoes.
The long white apron that Missy2U suggests is more bistro-style. The place I worked was more of a formal dining room.
A white shirt and a black skirt or pants is essential. I think a bow tie and apron definitely says “this is a waitress outfit.”
And make sure you take a white dishcloth (or something) and fold it and tuck it into the apron in the back for additional waitress authenticity. Don’t use a dirty filthy rag. That’s too much authenticity, IMHO.
Buon Appetito!
Be sure to wear a kerchief with green and red in your hair! 
Frizzy black wig. Snap gum constantly and wear too much makeup. A St. Christopher medal couldn’t hurt.
Was it Del’s? (or something like that)
Black pants, white button-down shirt, black shoes, a white long apron with the top folded down and inside so it doesn’t go above your waist.
Don’t forget a bad attitude and general disdain for everyone and everything. 
Nope. My best friend worked there. I refuse to divulge which place it was, 'cause it was totally a mafia front or something. But they were good to me.
Edited to add: in case that was unclear–My best friend worked at Del’s. I’m not saying where I worked!
you wanta some pepper?"
Cute. Omerta applies to the waitresses too.
I haven’t been to Bloomfield for awhile, but I grew up in the Mon Valley. I’m still an active social member of the Sons of Columbus in Clairton, and I know of an awful lot of restaurants like this.
Sorry, don’t want to see anyone wake up with a horse’s head in their bed. I just remember Del’s had some trademark food item that was served on every plate. Like a pickled carrot or something? /hijack