Everything in reach. Ever had surgery? There’s a reason that surgeons don’t roll into an operating room with a Kennedy box filled with scalpels, speculums and sponges. If you want to work efficiently, you should have all your tools under your eyeballs.
After working in lots of shops with a wide variety of arrangements, I have concluded that an optimal and realistic set-up is to have every tool – at most – one hand motion away from your eyeballs. Most of your tool set should be visible at all times. But the lesser-used tools can be one hand-motion away: Move a till to see a tool below.