Lists!!
I have an excel spreadsheet going back to 2001 (I skipped 2006 as I wasn't at work) with a separate sheet for each year to do presents ideas, purchases, budget etc. With 45 to buy for, and having made the mistake a couple of times of repeating "great" ideas for the same person, it's vital. (And I do the new sheet either in December, or early January, for the following Christmas, with a very rough indicative budget but also allows me to pick up things in sales and put them away but not forget).
I do the Holiday Grand Plan on Organised Home (a US website) which allows deep cleaning the whole house, 1 room per week, from the last week of August. And also does lots of reminders of prep for the holidays too (like - remember to buy baking ingredients, or get batteries, or check smoke alarms are working).
I have learned to simplify the Christmas celebrations themselves. (Sort of). We do a full turkey dinner when we are at home (rather than travelling and eating MILs turkey at midday, and DM's turkey in the evening, then rolling into bed!!). But only a couple of side dishes that we like, not 6 kinds of potatoes, 4 kinds of stuffing and 20 kinds of veg.
I generally prep the veggies and potatoes the day before, and boil the neck for turkey stock. And cook the spiced beef for DH. He makes the stuffing (he uses sausage meat, a la MIL, but DM never used that so I cannot do it - DH always has a lovely chat with MIL for about 20 mins each 24th as he reminds himself of how to cook the sausage meat and the seasonings needed!! 
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I have to work for a couple of hours on Christmas Eve (or take a full day's leave). It's a nice morning in the office, and I get parking in the city centre (public car park behind that I pay by the hour for - but it's mobbed by 10am whereas I get in early enough to get a space). So DD comes to the office with me and DH goes for nice coffee. Then we meet up once I can escape, and go get lunch and to M&S to pick up a birthday cake and a handful of boxes of nibbly things to use for DD's birthday on 26th. I only make sandwiches fresh, cook the nibbles, and we have plenty of soft and alcoholic drinks for neighbours and visiting family that afternoon (26th).
on 24th, after we get M&S stuff (the mad rush is usually over by lunchtime in city centre - still mad in our nearest suburb branch mid afternoon, we have tested both options over the years) and anything else needed from the shops, we head home. Potentially via the local park if the weather is nice enough and we are organized enough. When we get home, we light the fire (DD reckons Santa has magic to put it out - I'm not arguing!) and pop on nice music while I do prep in the kitchen. DD helps by making cookies (either from scratch, or just helping me slice off a roll of an earlier batch in freezer) for Santa later. We ALWAYS have a spare half batch of cookie dough in the freezer by mid-December to give us that flexibility.
Wrap early. I used to spend 3-5 nights slaving over it in late December and hating it. Now I try to wrap loads before the end of November. (And I have quite a few things that I need to post overseas, and also most years have to either drop things off near our house the week before Christmas if we are travelling, or have packages ready to drop off in our families' houses on a weekend visit between mid-Nov to mid-Dec if we are staying put for Christmas). I actually wrapped about 1/3 of this year's presents last Friday. Another poster on the countdown thread suggested using the ironing board for wrapping - genius!!
I write cards from October. Either a few a night watching tv, or if I have any trips, I do a load on the flights or train which is often otherwise "dead" time (and I don't usually want to look at work stuff then). Make sure you get the posting dates well in advance, and buy postage supplies (boxes, bubble wrap etc) and stamps (festive or otherwise) as early as possible.
I also keep a shoebox wrapped in Christmas paper (lid wrapped separately) under the tree. This looks like a present, but actually contains a roll of tape, scissors, screwdriver, spare batteries, spare bulbs for older lights (no need for newer diodes), and a couple of bandaids. Useful emergency things.
I have also learned to try and do the drudge work early, and have that finished by the start of December. All, or all except the last couple of small bits, of present shopping. Try and get non perishables shop done by mid December (when the 50% extra free and bogofs are out) or earlier. Have the house generally clean and decluttered, so that it's only minimal maintenance from mid December (quick hovering, quick dusting, swish of the mop, and a lick over the bathrooms etc). If you are expecting guests, I have sheets and towels clean and on beds early, and the room ready, and spare sets sheets/towels clean and put together ready to swop if necessary (changovers, emergency changes needed, etc). If you need to use family beds, just have the clean linens for guests ready and in a bundle to grab quickly the day you are doing the making up.
No matter how empty the bins are already (we pay by lift as well as weight here), I will put both the recycling bin and regular landfill bin for emptying just before Christmas. Recycling is always full anyway, realistically, but I'll clear out as much recycling as possible beforehand. Landfill, probably won't fill up, but I always want to have the option of space in it. And if recycling is full between lifts, I will either use the landfill one or we may take a trip to the local bring centre (not that local!).
Early December I will also buy in plenty of logs and coal (we had an open fire, now have a stove, and use it lots over the holidays). And make sure I add a pack of firelighters to the food shopping in advance.
I do internet food shopping relatively frequently, and while the week before Christmas is impossible to get slots, I will book one maybe 2 weeks out. This will have lots of things like bin bags, kitchen towel, toilet rolls, cleaning stuff (things that I would be likely to need over Christmas especially - washup liquid, dishwasher tabs, bleach - not things like window cleaner or leather cleaner), drain unblocker (in case of emergencies), stuff to make life easier over hols like part baked bread rolls, a couple of sachets of pre-cooked pasta and rice (Uncle Ben's, Dolmio) for fast solo dinners when there are overlapping nights out and fresh sauces for fast family dinners, and general storecupboard essentials. And heavy things, like soft drinks, fizzy water, washing powder...as well as the weekly shopping needs that week. It leaves me free to concentrate on other things when I do the shopping in store the week before Christmas (both brain wise and trolley space wise) - the more festive things and fresh things.
I try to have at least 3-4 dinners for the family in the freezer to use over the month of December. And a number of single portions too (see overlapping nights out). So I'll make 2 lasagnes sometime in November and freeze 1, a double batch of a couple of curries and a spag bol sauce (freezing half each), and maybe something like a shepherd's pie or smoked fish and broccoli pie. And/or have a few things bought in but frozen to do the same, like a good quiche, pizza, chicken kievs, oven chips, and frozen veg. Make it easy on yourself.
By prepping early, and having solutions for meals etc on hand, it means I can concentrate more in December on the manic work life, getting to enjoy a couple of nights out (work - main night for all staff and a small section lunch extending until late evening, and I might manage to meet up with a group of friends who started work together years back, while the wives on our street all like to go for a meal locally too) and allowing DH to enjoy his nights out as well. And we also get a decent chance to be able to have enough energy left to enjoy a date night ourselves, and a couple of family things with DD (she has a few parties from sports clubs, a Christmas tournament in hockey, my office Santa party, and we always want to do something just as a family too). This year, we are going to a Carols by Candlelight concert on 23rd December at night.
It is also very important to organize being sick. Sounds daft. BUT. Have all scripts filled. Make sure you have cough, headache, upset tummy remedies etc on hand to reduce miserableness of anyone afflicted and keep it at bay for the rest of the family. Eat healthily and get some exercise in the run up to be able to keep your own energy levels up. Do NOT overschedule the family so that you keep all the energy levels reasonably balanced. Take a few minutes every day to recharge, have some nice smells around (essential oils or scented candles are great, but even just festive cooking, fresh pine, or nice air fresheners/pot pourri or whatever). Get fresh air!! (Hang washing outdoors, walk pets, bring the kids to the park for 20 minutes to run around).
Nothing is worse than a totally frazzled Mum, Dad, or worse, child (of any age!) on Christmas Day because they have done too much prep work (in total or at the last minute). So simplify the days of Christmas week, and either prep in advance or don't bother. The warm atmosphere with forgotten crackers or 3rd kind of extra sauce is much more memorable than tears, tantrums and frostiness of a "perfect Christmas where nothing is forgotten" but at least 1 person is too stressed out.