You don't always have to take on a big project to kick off your minimalist journey. The important thing is to just start, even if it's something small.
It's also the small projects that are overlooked the most -- when was the last time you looked in your wallet!?
I find it's almost always a place of clutter, chaos, and unnecessary "trash", which is why I recently cleaned mine out.
After a few minutes of sorting (really, that's all it takes!), you should be left with the essentials: driver license/ID card, debit/credit cards, insurance card(s), and a little cash.
But what about the other "stuff" that no longer has a home? Here are some tips on what to do with it:
Receipts: See this post on which receipts to keep (and for how long).
Business cards: Don't store them in your wallet and let them take up space! Take a picture of it with your phone or enter the info into your contacts right away and then toss it.
Gift cards: How many times have you had a gift card and couldn't remember how much money was left? There are a couple of phone apps out there, like Gyft and Go Wallet, that can help you keep track of that info. A lot of these apps also allow you to get rid of the card completely by generating a bar code (if using in-store), but double check with each retailer before doing this.
For more decluttering projects (both big and small), check out my minimalist book Minimalist Monday: Declutter Your Way to a Zen Home (You can order it in all electronic forms (PDF, Kindle, Nook, etc) here.)