Help me wire a hypothetical lathe and mill

When I walk to the SE corner of the shop under construction, I can almost reach out and feel where the lathe should go. When I'm standing at the imaginary lathe, the imaginary mill is right behind me. However, I need to do rough wiring before final structural inspection before drywall, all of which will happen before actually acquiring any machine tools... Help me get the roughed-in wiring which will eagerly await its matching tools right so I don't regret all that drywall...

Is 30A 220V a good guess with reasonable overhead for anything likely to wind up in a home shop? A little searching suggests this with 12g wire as suitable for up to 5hp... Do I need a bunch of add'l capacity in case I wind up with a 3-phase tool and a phase converter?

Guessing I need 12/3 (as opposed to 12/2) wire so there's a neutral so 110V accessories can be fed from the tool?

It seems unlikely that I would run the lathe and mill at the same time... But is it foolish to put them on the same circuit for the savings of 60' of 12/3, a breaker, and some time drilling studs? (which reminds me I need to look up the requirements for whether I can have any of my misc romex runs sharing holes...)

And while this specific question is important, it's not like I'm going to turn down further shop wiring advice. We've talked about it lots of times here, but often some new detail will turn up (or be brought back to mind). And yes, I was just going over Tom's summary, which made it feel delightfully simpler, but I still hope to avoid shooting myself in the foot and I'm sure there are details not covered in that article (e.g. machine tool specifics to bring us full circle...)

Code books and code-summarizing simplification books for the lay person are excellent, but insight and advice will help me avoid applying perfectly good info incorrectly...

Have you looked at any lathes or mills yet?  Most any machine used by a shop has a strong chance of needing 3 phase power and not simple 220V.  I bought a Logan lathe over 20 years ago and the motor required 3 phase power. I bought a phase converter and wired up 220V per the instructions and the machine has worked great ever since. The wiring requirements are to high. I used 10G wire. Better to over size then to under size. When I wired my air compressor I also used 10G wire pulled through thin wall conduit as that's what the local code required. 

I ran one 50A 240v circuit with a plug right next to my panel, and one 30A 240v circuit with two wall plugs on opposite walls. Combined, these three plugs give me a source of 240V centered on three of my four walls, and I haven't wished for any extra at any point. I ran separate circuits for my lift and compressor, with each getting its own 30A 240v circuit. This is technically overkill, but makes it easier to expand in the future. IIRC, I used 10/3 for the 30A circuits and either 6 or 8 for the 50A circuit. I erred on the side of too large to futureproof my runs. I also ran all my 120v circuits with 20A breakers and 12/2 wire, which has been awesome. I've never blown a breaker by having too many things plugged in. 

Yes, always pull a neutral through with whatever you're running. It adds nearly no additional cost or labor, but you'll be so thankful when you need it. I wouldn't be able to have a 120v plug on the side of my Bridgeport, for example, if I hadn't pulled a neutral through with the 240v circuit.

A few other observations: Put outlets, both 120V and 240V, near the garage door. I have one of each between the two garage doors on my shop, and use them more than any other outlets. Put extra outlets on the ceiling, too, as they're handy for garage door openers, cord reels, lights, etc. Don't forget to run circuits for exterior lighting--I wish I'd run more. And don't forget outside outlets, too. I put two on the outside of my garage, but if I had to do it over again I'd put four or six on there. One thing I did do well was to consider the path of cars and people through the garage, and place outlets so cords wouldn't be in the way. There's a two-foot corner that separates the side door from my garage door, and I'll be forever thankful that I took the extra 20 minutes to run a 120v circuit to it. When I plug a battery charger in, I don't have to leave its extension cord across the door, so I don't have to worry about tripping over it.

Overall, my garage wiring was definitely overkill, but you don't need to use any extension cords to work in it, and that's worth every bit of money/time/sweat I poured into the wiring. 

EDIT: Don't worry about three-phase machinery. Any machine you're putting into a residential garage will probably be fine with a cheap VFD and a 30A circuit. 

A couple of things to keep in mind, breakers, wire and plugs/receptacles are all only rated for 80% of their rated power so your 30 amp circuit with 10 awg wire is actually good for 24 amps (15 amp circuit, 12 amps). 

For the single phase to 3 phase conversion divide your three phase amps by 0.577 and that will give you the amp draw on the single phase side of things. That is also used for sizing your VFD if it is a 3 phase input/output drive (single phase input drives will already have the sizing matched, 3 phase input drives will work though). So, say the motor on your shiny new lathe has a full load amps (FLA) of 6.75 amps then that motor will draw 11.7 amps on the single phase input of the drive, you would need a 3 phase drive with an input rating of at least 11.7 amps to handle that motor. It's a good idea to have an amp or two of extra capacity for losses in the drive.

I have a detached garage/shop.  When I upgraded the feed it was a 100A 230V feed.  I've never needed more but I have a 5500W electric heater, a 3HP three phase mill, a 10HP three phase lathe, a 40A single phase TIG welder and a 2HP 230V vertical belt sander.  The lathe routinely draws 60A for a short time spinning up the chuck but rarely draws 20A while in use.  While not everyone needs a 1950s vintage 10HP 6000lb lathe in their shop, I highly recommend it.

As a single person working I'll never need more than one of them running along the with the heater but I heartily recommend putting more than you need in now.  It will never cost less than doing it once.

I don't know if it's legal where you are, but every outlet run I put in was with 14/3 and a dual breaker with each outlet split so there were two circuits on each plug.  The huge benefit is when I wanted a 230V outlet somewhere it was just swapping a receptacle and coverplate.  Also, put in twice as many receptacles as you think you need.