We run low-temp washer fluid year-round and none of our vehicles call for different oil in the winter. All our services are up-to-date, there really isn't much that needs done to prepare for winter.
I no longer switch the A8 to 476S and I don't really do any winter's-coming extra detailing; they're all in maintenance mode already.
I do put heavy-duty mats in the dog-haulers so we don't have to change out of our winter boots.
Everything I'll be driving regularly gets winter wheels/tires (even the AWD vehicles) and BHB-equipped window brushes/scrapers.
(Hmm...haven't decided if I'll be driving the DenaliXL in serious weather, it's mighty nice right now and awfully big to redo

Oughta start shopping for winter tires if I'm gonna really use it, already have spare wheels.)
Other than that we just remember to take heavy warm boots/clothes if we're dressed up, just in case. We always assume that any vehicle can leave us stranded at any time, better safe than sorry, so we have emerg. stuff with us anyhow.
Take your cell phone and keep it charged.