There's a lot of good tips here,,,, but where's you guy's pictures??? Ain't ya proud of your shops???
My shop is a Vargus Purdun all metal 42x50x12.
I like a drive thru design but I killed my drive-thru when I added a hoist.
I like a square design rather than a long narrow design.
Don't get cheap when you pour concrete, in my area 6" minimum. I poured 6" on top of 1" gravel so I've got closer to 7" strength. No cracks. Also pour a stepped drop in the doorways. Let your doors shut down into that step. No water blows in under the doors.
I like a flat floor as mentioned above for fab work. A floor drain for me just becomes a catch all for that loose washer, nut, spring, clip, etc., that gets away from me.
When wiring the shop go completely crazy, plug-ins everywhere you can hang one. Welder plugs on each wall at a minimum.
Bathroom is a necessity. Not just for the luxury of the toilet but more for the luxury of running water. Beats the crap outta washing your hands outside under the hydrant in the middle of a snow storm. I also have a refrigerator next to the bathroom with an ice maker plumbed off my water supply.
I put my air compressor in the bathroom so it's not so noisy. Plumb air drops until you get sick of installing them. I also added a 50' air hose reel in the center of the shop ceiling. Another sweet trick, I wired my compressor to my shop lights. When I walk out at night and turn off my lights, I also turn off power to my air compressor. Cost $50 for a magnetic starter to accomplish that.
Go big on the doors. A 10' wide door gets extremely narrow extremely fast. Buy good insulated doors. I have CHI doors. Have at least one automatic opener. My doors are 12' wide x 10' high. I have three.
Buy good, big, insulated glass windows and put one about every 10-12 ft of wall space on all four sides. If during the day you have to turn on the lights to work,,,,, you didn't buy enough windows. Also a must have is a window panel in each roll up door. I even have half of my walk-in glass.
Buy good lighting. I used 8, four tube, four foot long, T-8 fixtures. $1K in lighting fixtures. Looks like a space ship parked in my backyard at night when the lights are on. If I ever need a trouble light I can't find it cause I rarely need it.
If you're gonna build a shop don't let money tie your hands too much. And don't even try to tell me how you can build a big shop for a few thousand dollars, ain't gonna happen. Okay,,,,, wait,,,,, yes,,,, you can build a 40x50ish sized shop for $10K. But it'll just be a metal pop can building that's worthless in anything beyond perfect weather conditions. If you want a year around shop, expect to spend as much money finishing the shop as you spend on the initial pile of building materials.
I'll admit it since no one else will, we have $41K in our shop minus the hoist. My Sons and I built it but hired the concrete poured. The building laying in a pile in the yard was $20K. So we spent an additional $21K for concrete, wiring, plumbing, 100K btu furnace, bathroom materials, etc.
Do overs. Would add additional winter insulation kit and completely cover inside walls/ceiling with metal. Would have added another $3K.
We lost our shop in a fire 2 1/2 years ago and this is what we built back. When my Sons and I were standing on the spot of the old shop after we'd cleared it off they said "Dad you should build the shop of your dreams to replace the old one". So I did
So here's some pics of what my wife affectionately named the "Man Cave". I am so truly blessed. When we were standing in the yard watching our old shop burn down my wife hugged me and said "Honey, why couldn't it have been the house". I am so blessed.