The Simple Dollar blog today offers up six tips for optimising your wallet to help form good financial habits. There are a couple of suggestions for minimising your spending (cut down to two credit cards, put a picture of the goal you're saving for by your credit card to help you cut down impulse spending).
I really liked the suggestion that you treat your wallet as an 'inbox' which you should process and empty on a regular basis - say once a week or once a month. Given that most people keep their receipts in their wallet, this will help stay on top of finances and reduce wallet clutter.
Wallet Hacking [The Simple Dollar]