I start shopping in January. I will buy next years cards and wrapping paper, which always ends up being expensive just before the event, and some generic gift sets from Boots or Body Shop dead cheap for colleagues, childcare workers, those type of people. Id rather get them a £20 set for a fiver than a £5 set in a panic.
I never pay full price for anything, unless its a very specifc toy my youngest has asked for. Even with DD1 now, who is 12 two days after Christmas, I will say to her that Santa probably wont get that but I would be happy to get it for her birthday if she can wait and we will go shopping for it (if I am sure an item will be in the sale). She obviously does know about Santa, but we still play the game!!
I use Pricerunner, Kelkoo AND Google Shopping to check prices for absbloodylutely everything. I wait for special shopping events at Debenhams and House of Fraser, etc. Play.com deal of the day has been good this year too.
I buy food which is nonperishable in the run up when I see it on special. Ditto wine and alcohol (got my litre bottle of Baileys for £10 several weeks back, as an example).
I buy everything on my Play.com credit card and convert the points into play voucers (you can get an Amazon one too). I pay for my food shop on a Tesco credit card then convert the points into 4x Goldsmiths vouchers. I DO the food shop in sainsburys and get nectar points too which then translate into free toys from Argos.
I try to write a list and not be distracted from what is on it (but I find that hard). I book meals out and order food a good bit in advance, paying deposits, so its not such a whack all in one go.
I collect vouchers from papers. I begged borrowed and stole Sun Perks from colleagues and got some free DVDs. I collected the Mail Rewards at the weekends (I always buy papers anyway, otherwise its not a saving at all) and Ive had £5 Tesco vouchers, £10 Boots vouchers, £30 high street vouchers and Downton Abbey series 1 dvd free this year.
My luxuries - a real tree every year, whatever the cost, and a lot of baking. Its actually much cheaper just to buy ready made. But I love doing it.