Well, when I say ultimate .... 
But while the list isn't exhaustive, I hope you find it a good starter for ten.
Don't forget to post with details of anything I've missed!
Things to start doing, um, now, actually!
•Write gift lift and set your budget
•Write (and post) xmas cards
•Order xmas tree and make note of collection date.
•Write a food and drink shopping list
•Pre-order shop-bought items eg. xmas cakes; puddings; anything else fancy!
•Buy non-perishables (
, nuts, gin, sweets, more .... !) so you can tick off your list and feel organised
•Secure a supermarket home delivery slot (they go quick!)
•Start gift shopping (and don't forget the gift wrap, tags and other bits and pieces)
•Wrap gifts as you go along (if you don't want to be up until 2am on Xmas day)
•If buying online, don't forget to shop using a cashback site (eg. I personally use kidstart)
•Post international xmas gifts and cards
W/c 1 December
•Put up your xmas tree (this is when you wished you'd pre-planned a colour/theme - so add that task further up list!)
•Book hair and beauty treatments so you look presentable for the big day.
W/c 8 December
•Put up xmas decorations - inside and out (but don’t worry if you couldn’t wait and have done this already!
•Clean the house (or find someone to do it for you - local.mumsnet.com/enfield/cleaning-services)
W/c 15 December
•Produce a food preparation plan, complete with timings for cooking/preparing meals for the three days
W/c 22 December
•Buy fresh food (probably best to do the day before). Don’t forget the food for Santa and his reindeer 
•Buy batteries. Lots of them. (We’ve all been there!)
Christmas Eve
•Pour yourself a tipple of your choice, sit back and marvel at how organised you’ve been this year!