I hope this doesn't come out as one long paragraph again.....
We usually put the tree and decs up on first Saturday of December. We make a whole day of it. Have a good spring clean in the morning, then stop for lunch, then decorate while watching The Santa Clause. We all have baths/showers then have a beige buffet for tea in front of the x factor.
The day before decoration day on the Friday I always put all the Christmas bedding on the beds while kids in school and dh in work and leave a surprise out for everyone. Last year we all had festive slippers/bed socks left on the beds.
Ds is the only one who still believes (at the mo anyway, just turned 10 and going into year 6 so who knows what might happen between now and Christmas!) So we take him to see Santa at our local garden centre which is amazing. Wish I'd known about the place when my girls were small!
The three kids have small stockings hanging on the fire place. Every night their elves leave them a small treat - usually a festive choc of some sort and sometimes a festive pen or similar. Ds has a letter from his elf as he still believes.
Every year I buy a new elf door. Once decs are up and ds is in bed I blu tac the door somewhere for him to find. It's how they get it and out!
This year I'm going to book Christmas Nights at St Fagans. It's a local open air museum and it's a lovely festive night with live band playing music, stalls, crafts, etc. We went a few years ago and loved it.
I always stock up on festive silliness for parties such as face mats, Christmas quizzes, pin the nose on Rudolph, last year I bought a fish bowl for the adults, I make vodka jelly shots for parties, we play charades (the kids version so they can join in), Dobble.. ...lots of different things. This year I've bought dh an inflatable Santa suit and myself an inflatable turkey suit for when we host any parties.
I now own (I think) 9 or 10 festive jumpers and 2 dresses. This is my uniform for the whole of December. Even on the days I work. Dd1 (soon to be 16) thinks I'm an embarrassment 
Christmas eve the elves leave us all a few pressies. Always new pj's. And usually something like new festive socks to wear out that day when we visit the in-laws.
Throughout December we do the usual baking, writing cards, watching festive films (every night!), hot choc with cream and marshmallows......
I find it all exciting!