h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Don't be fooled into thinking that 24 hour opening means you can shop at the last minute - the shelves will be empty by then.
Buy non perishables as early as possible & avoid too many perishables, there's nearly always far more food than people will eat.
If you do a supermarket shop within 2-3 days of Christmas, take a cool bag to put cold items in straight off the shelves & take a book to read while waiting in the checkout queue.

Write a list of what you think needs doing (food preparation, present warpping, cleaning, tidying, bedmaking etc) to make sure you don't miss anything vital. Draw up a timetable of what to do which day, prioritise & delegate where possible. Make sure that if anything is likely not to get done, it will be something you won't worry about.

Do a more detailed timetable for the big day, to start things cooking at the right time etc.

If something gets left out, so what - improvise or do without. If you cooked, leave the washing up for someone else.

Remember that eventually everyone will go away again!

If the programme does start to fall apart at the seams, there's always sherry to fall back on.

What Christmas Dinner is complete without the hostess piping up with "ooh I forgot to take the chipolata sausages out of the oven" just as everyone is mopping up the last of the gravy?