Plan you menu well in advance, this way you will know in good time what food you can buy in advance, what needs to be ordered (hams, seafood for example), and what needs to be bought in the days before. Start buying non-perishable items from about October. This will distribute the expenses across a couple of months, and help to avoid last minute, mad rush, and enormous volume shopping trips.
When planning the menu, consider whether to not you intend to include the following:
- Drinks and canapés
- Entrees (will you need bread plates, soup bowls, small plates?)
- Main meal
- Salads and side
- Sauces and gravies
- Desserts (cakes? Ice creams?)
- Cheese platters
- Sweets (as in lollies, slices, biscuits, small cakes)
- Tea and coffee?
Once the menu is set you can work on a baking a cooking and schedule for Christmas. This way you can plan to make or bake items before Christmas Day (or the function) and keep down the amount of actual on-the-day cooking required.
Here is a handy Christmas Serving calculator from Taste.com: How much should I serve