The more ceiling height the better. Mine's 11'6" and it severely limited my choice of lifts. I got a Ben Pearson 9000ADJ (the ADJ stands for adjustable height) and at its tallest setting it just fits. I still get full height and can walk around under a car no problem.
Almost every lift manufacturer specifies a minimum 4"-4.5" slab thickness for proper lift mounting (for a 2-post lift). Keep this in mind when spec-ing out your slab.
Don't forget the 220/230V outlets! Most welders, plasma cutters, etc. have somewhere around 6-15 feet of power cord.
Here's one to think about -- I have a large steel I-beam running laterally across the ceiling. Pop on a trolley and chainfall hoist and you've got a rock-solid engine hoist. Pros: not screwing with the cherry picker. Cons: can only translate side-to-side, not forward and back. You have to roll the car for this. If the car's not a roller....OK, I still use the cherry picker a lot.
I've got one 30+ foot wall that's all cabinets with workbench on top, then pegboard, then layers of shelves all the way to the ceiling. The shelves are hung from the beams above, not the wall, so they can hold heavy items. You have to use the ladder to get to them, but that's fine for longer-term storage stuff.
For drainage, I've got a ~4" x the entire width of the garage drain with a grate over it right inside the overhead door. Makes for easy hosedown & sweepout. Oh, also key to the hosedown thing is having the bottom foot or two of the wall be cement blocks or similar before the drywall starts.
This bad boy keeps me toasty on the coldest winter days (it's been in the single digits lately in the morning here). It's gas-fired and has a thermostat for control.