I'm with Adirondack. I like having a lot of gear ready to go, but most of it stays with the truck. I carry a magazine pouch that I can clip to my belt. It has one box of flies, an extra leader, and the stream thermometer in it. Attached to the outside by two retractable lanyards are are a leatheman and a folding box cutter. Wrapped around the bottom is a stringer, that is rarely, but recently used. I put my floatant and tippet spool in my left front pocket, sunglasses on my head, liscence, I.D., and truck key in a closed chest pocket. If it is a warm day, or I am going to be gone from the truck for a little while I throw a full camelback on with a warming layer strapped to the outside and I am ready to make like a horse turd and hit the trail.
Life is hard. But it's a lot harder if you're stupid.