Here is something they don't teach you in school: Wallet Organization.

When I first read Nudge. I realized the importance of product placement, power of rewards and making useful choices easier to make.
I wanted to slim down my wallet to ease the bulge in my pants (Stop that thought right there.). I sat down to the chore of organizing it. Slowly it all came back to me a epiphany. Here were some of my goals,

1. Wallet should be slimmer but I need everything with me, No compromises.
2. Arrange my wallet in such a way that its easier for me make good choices, like picking up that Debit card among my several credit cards.
3. Make most commonly used cards fastest to access (80 - 20 Rule) 

Firstly, 

They can make all the noise about the electronic wallet, phone replacing everything. Its not here yet. But how can move some of the bulk from your wallet to phone? Get rid of all the cards which you rarely use but you need them, like all the rewards cards. A simple picture will do. But wait, isn't it hard to find them among all the photos of the cute/weird dogs, cats, girls. I used to Evernote to organize the pictures of my AAA card, B&N Card and Super market rewards cards in a more book called cards. Mission one accomplished.

Secondly,

Those wily Discover Card designers. I found myself using Discover very often, but why? I started to think about it, they made it easier for me to find a card. Edges of the card are painted in orange so when you are looking at an array of cards with white edges this is bright and easy to spot. It gains your immediate attention. So I did that bastard away. I placed my debit card and Metro card on the top so its easily visible and quickly accessible. This has significantly changed my spending habits.

Lastly,

Even when there was enough space for me keep all the cards readily accessible I hid them away in interiors making it harder for but the fact I am carry them all the time with me, made it convenient enough for me to get to them when I wanted them.