I did it for the first time last year, and my one piece of advice would be KEEP IT SIMPLE. I balk at all the magazine articles that suggest you jazz up your vegetables. I can't begin to imagine why you would want to fry up bacon and chestnuts to serve with your Brussels sprouts, at the same time that you're trying to crisp up your roasties, get the turkey out to rest and get started on the gravy.
If you do fancy trying something a bit adventurous, make it in advance and freeze it so that it just has to be heated through on the day - ideally in the microwave to free up oven/stove top space. You'll have the extra hassle of simultaneous vegetarian/ meat-eater menus, so you really will have to plan ahead to make sure everything's ready at the right moment.
Don't serve too many different vegetables. But stock up on some bags of frozen veg in advance so if you have a last-minute crisis of confidence that you haven't done enough, you can just bung some extra peas on.
Don't be too bound by tradition - if everyone hates sprouts/ Christmas pudding - then don't serve them. Make the most of the opportunity to try something different.
Go with the flow -especially if you have young children or difficult family members. Timetables are useful, but not everybody wants to stick to a rigid schedule on Christmas Day. Cook the turkey first and then get it out to rest. Then wait until you're sure that everyone is ready to eat, before putting the veg on and heating anything else through. It doesn't really matter how long the turkey is out for - it won't go cold if you wrap it in foil and a teatowel. And you can always warm it up with the gravy.
Be honest about what you want to do. Don't flog yourself serving up a homemade meal if you absolutely hate cooking. Pick and choose the bits you'll enjoy doing and buy in the rest. Nobody's handing out prizes.
Hope it goes well. I'm looking forward to a calmer, more relaxed Christmas lunch this year.......