...is that if you're going to have a sink, you need hot water. If you're going to have hot & cold water you may as well have a toilet and a small shower. So I ended up with a janitor sink in the shop and a small 3/4 bath. If I get to having train meets here the cinder sniffers can clean up before returning to polite company. (Plus if the shop ever becomes my doghouse I'm already set with bath, sink, refrigerator and microwave!)
Think about light as well, I put in a lot of light fixtures but still have separate task lighting around machines and welding. The fabrication shop really doesn't have enough lighting, and the fixtures I do have are dim for a while when it's cold. I did put in a 100K BTU unit heater last fall that can warm it up but only used it a few times this winter. It takes it from 40 degF to 60 degF in an hour, you might want to consider that.
In the shop I put 1/2" plywood on the walls, this so I can just put a VFD or shelf up where needed. I'm waiting for a great deal on wall mount cabinets so I can cover the walls with them, the real problem is that most of the ones I can get cheap are just that - cheap and not worth it. That and the expected use (tooling storage) means that I'd be putting 200+ pounds in most of them. Maybe it's time to get the table saw I've been looking for and make some of my own.
Leave a few empty 1" or better conduit into the breaker box when you're done. You'll pull additional lines and will be glad there was easy access.
Make all your outlets 20A, and split the circuits on the duplex outlets. Put in more duplex outlets than you think you need.
I ran a 3/4" air line loop at the bottom of the ceiling, and put in 8-10 drops down from there. I used the Rapid Air pex-al-pex line and their fittings, kind of spendy but I can now walk no more than 15 feet and have compressed air. I should have put in more manifolds in the shop since I have permanent connections for the mills and lathes, that's something I'll have to fix sometime.
I really should have put more time in the design and layout of the shop beforehand - like the light switches and locations. They're generally "ok" but a few oddities that would cost more to fix than they're worth - like the one porch light that switches with the front floods instead of with the other 3 porch lights - should have had all 4 on a 2-way.