Basically, like any christmas club you contribute during the year and jsut before christmas you get your money back - a great way to save for those of us who aren't so good at it.
But Myer are going to give you 10% extra.
FAQ here - www.myer.com.au/resources.ashx/Files/611/File/E36B6AE65CAE4104D4BE4481A84FEFB8/MYER_Christmas_Club_FAQs_MARCH_2012.pdf
The cards will be delivered in November 2012. You need to set up a regular payment plan and $20 per month is the minimum (or $10 per fotrnight). Catch is that you will need to spend the card at Myer, but they do match prices on same products. THe cards will be valid for 24 months.
I'm planning on buying a food mixer later in the year and at $429, I figure I can buy say $300 in the Christmas club - they'll give me $30 extra - then if I wait for a 15% off sale once I have the card - my mixer will go down to $360! (and Myer will have paid $30 of that for me!)
If you're super organised and a regular shopper at Myer, you could do this every year, then spend the next year spending the money 9and you won't get 10% on savings in that same time)