OK, theatergoer: You’ve silenced your cellphone, unwrapped your candy, and shushed your seatmate. Nicely done. But how are your table manners? Well, get ready to put your napkin in your lap and seize your appetizer fork as you dine out on Richard Greenberg’s new show, The Assembled Parties. As with the earlier Three Days of Rain, this Manhattan Theatre Club show moves between decades and generations. Initially set in 1980 at a Jewish family dinner on the Upper West Side and then jumping 20 years into the future, it concerns the changing fortunes of the wealthy Bascov clan, portrayed by the likes of Judith Light, Jessica Hecht, Jeremy Shamos, and Mark Blum. Lynne Meadow directs this multi-course drama.