Try banning EFTPOS use for any non-budgeted purchase. Now that you have your essential's budget (groceries / bills) Draw out the set amount of cash you have decided for you and DH's miscellaneous funds for the week and only use it like an 'allowance'. Have to implement this with my DH as I went through our bank statement and it is amazing how much those little things like a takeout lunch, a cd, alcohol & dvd hire cost!

EDIT: I budget $200 for our weekly groceries, bathroom accessories and includes formula etc but not nappies as I'm a clothie - I find I can always meet that budget I shop at ALDI, the chicken shop and grocer. If I shop at our local COLES I have to be super selective as it can blow out by $50. HTH