I keep more than I probably should; but I also overpack when I go camping.
Shirt pocket: notepad and pen
Front pant pockets: truck keys (my car keys stay in my bag and I stopped clipping the work keys to my shirt awhile ago) and usually random stuff from the course of the day
Rear pant pockets: Wallet
L cargo: I try to keep empty so I lay on that side and so that collected wrappers, extra rhythm strips and electrode backings from call go in a little baggie there and then the garbage rather than get left on scene or tossed in an equipment bag,
R cargo: Penlight, pen and shears in their appropriate slots on the pocket, service field guide, pocket pharmaceutical guide. (Been looking at some great cargo pocket organizers, so that I can leave the stuff on the dash with my steth and just toss it in my pocket when the tones go off)
Belt: Phone, mini leatherman.
That's what's on me for every call; my duty bag has my various issued PPE (the trucks are all stocked as well of course, but to ensure we are never without PPE we are all given our own boxes as needed), flashlights, helmet, info for pt.'s families on community programs or the local hospital locations, hard candies and granola bars, extra pens, camp pillow and blanket (for standby's), a pathophysiology book, Merck manual of Patient Symptoms, novel on the go, copy of the Collective Agreement, rain coat and ANSI vest.
This is the pocket organizer I've been looking at.
http://www.candfsupply.com/index.php?main_page=product_info&products_id=255