I tend to vary the bourbon (Maker's Mark still a favourite). Used to use Cinzano 1757 but currently either Cocchi Vermouth di Torino (v. good) or Carpano Antica Formula (absolute winner!). Stopped using bitters as found it just detracted from the complexity of high quality vermouth. Best to date is about 60/40(-ish) Maker's Mark/Carpano. Definitely Luxardo maraschino cherry (maybe a drizzle of the syrup). Clementine twists add a hint of Christmas. Slight dilution by the ice not a bad thing.