This is what I do...
Have a Chest freezer and a big upright fridge! Makes life a million times easier.
Pack away this year's Dec's carefully so next year you won't be untangling fairy lights! Label each set, so you know which goes where. Eg outdoor tree.
Download a gift list app. With a budget for each person.
Work out how much you will need to spend (include events here) and divide by 12, then put this aside each Month.
Plan with family and friends who will be hosting and when/where. Also who will be buying presents for whom or would a group secret santa be easier.
Have a Christmas shelf where you can put items as you buy them.
Buy gifts throughout the year when you see them at a good price. Wrap them as buy them and tick them off on your app.
After a disaster with a posh turkey a few years back (it was rotten) we buy a frozen bird. It's half the price, no one notices its not a £120 fancy git.
Aldi champagne is amazing (That Gilly Goulden agrees).
Forget Delias cake recipe, the sainsbury 5 ingredient one is gorgeous and really easy. Make it in Nov and keep adding Brandy. Dont wait for Xmas day, eat it through December as no one wants Xmas cake in January. (Same goes for mulled wine and posh biscuits).
For food/alcohol have a list on the computer that you print out each year, then tick off the items as you buy them and put them in a "hamper" marked Xmas (so the teenagers don't eat them).
Freeze lemon slices for Gin but buy ice, life is too short to be making ice cubes.
Make and freeze a big fish pie or lasagne for Xmas eve.