OK then -
Make cake, puddings etc.
Buy things like advent calendars, tree crackers, other crackers, tree chocs, any other decorations.
Order/ buy tree if real one.
Order turkey/other meat/poultry from butchers.
Buy presents, cards, wrapping paper, gift tags, sellotape.
Write letters to go in cards for people you don't see, and only write to once in a while.
Wrap presents and post those that need it.
Plan menus, do advance internet shop for bulky stuff etc, then write lists for other food shopping you need nearer the time. Don't forget things like foil, batteries, spare bulbs for tree lights etc.
If having people to stay, make sure you know what sleeping arrangements will be, and that you have enough bed-linen, towels etc.
Nearer the time, I usually do a timing list for Christmas dinner, so you know what needs to go in the oven when, etc. Also you can make some things ahead and freeze them (e.g. last year I made soup, quiche etc for use over festive season, froze them and thawed when required. I was really glad of this when I was ill on Christmas Eve, and could just say to my sister "Heat quiche in oven and bung together a salad with the ingredients which are in the fridge" - instant supper!)
Errrr - is this enough to be going on with?