I have two credit cards, two subway passes (monthly and stored value), my ID and insurance cards, and a “wallet-style” (folds vertically to go in a credit-card slot) book of stamps in my wallet (also a couple cookie fortunes 
). It’s all of a quarter inch thick. Cash goes in a money clip in one front pocket, along with chapstick and nail-clippers (I’m a little OCD about my nails) and a very minimal set of keys–building, apartment, mailbox, office desk, utilikey, a couple barcode tags. (Bike keys and SO’s keys live on other rings that get pulled out of a drawer at home when necessary.)
The other front pocket stays is free for my iPhone, and I don’t have to worry about scratching it.
Quarters go in a bowl at home to be saved for laundry; all other change gets spent ASAP, or thrown in communal change piles at work for those times when I need an extra dime to make the price of a soda.
A Leatherman wave lives on my belt in horizontal position, and I keep a d-ring hanging from a belt loop on the other side–handy for hanging a light bag of groceries or an umbrella for a minute to free up a hand.
