At the moment my wife and I share all our bank accounts - although we're changing that next month to give each of us a bit more independence - so anything I buy her for Christmas will be obvious to her because she can see the purchase.
So I sat with her while she bought some clothes for herself from a specific shop, and when she showed me one of the really nice things I said I wasn't sure about it, so she took it off the list.
Then as she made her purchase from one of our accounts, I bought the nice thing from the other account, because I know she won't notice that the same payment came out of both accounts at the same time.
