Your tool belt keeps your tools, nails and screws at your fingertips on the construction site. It should be durable and comfortable to wear. I've learned to keep my hammer, tape measure, layout square, pencil, eye protection, ear protection, and two sizes of nails in my tool belt at all times. The building process is easier when you can find what you need quickly and easily.
It took a few adjustments, but I've come to appreciate my Bucket Boss tool belt. The Builder's Rig has a padded belt, metal hammer loop, quick-release belt buckle, an angle square pocket, and multiple pouches for your stuff. I removed one of the big pouches because it was too bulky. That puts my hammer at my right side and the one remaining big pouch on my left. The small pouch is at my back and I use it to hold 8d nails. 16d nails go in the smaller pouch that is attached to the big pouch, and everything else goes in the big pouch. It works for me.
Bucket Boss makes heavy-duty stuff and this tool belt is no exception. It's not expensive either -- about $35.