clarification:
external garage = detached garage.

I made a typing mistake above. Grounding on the neutral should read grounding on the ground in the sub-panel.

You need to run a separte ground wire to the sub panel.
The neutral needs to be isolated from the ground.
You need ground rods at the sub panel.

It is not requirued, but I would run a green wire for ground in the conduit within the garage. You only need one per conduit sized to the largest circuit. All the other circuits can share the one ground.

JoeD is correct. Your garage needs a grounding system (typically rods). If you run any other metallic circuits the ground wire with the feeders is required (any phone, cable TV, networking, etc...). Even if not strictly required, it's a very good idea. Florida seems stuck on the 2005 NEC right now, but the later versions of the code no longer allow you to skip it either.

by the way. I am using all metal boxes (switch boxes, outlets, Junction boxes)...they cost more. Is it permissable to use plastic boxes for the junction boxes and metal for the switches. My reasoning for using metal was for anything below the ceiling that could be damaged by flying car parts.

In my experience working on cars, there is not telling what will get smashed, caught on fire, or bumped hard. One time I had a spring compressor fail and launched a coil spring at high speed into the wall. Fortunately no one was in the path of the spring. (I have sinced developed a technique better than the tool).

Keep the constructive comments coming.

Assuming that there are no local code modifications, you may use either plastic or metal junction boxes at your discretion. Neither will provide much protection against high-speed flying coil springs. Remember that if you use metal boxes, the ground wires need to be connected to the box using a grounding screw.

For the 240V/30A circuit, you'll need 10g wire. If using NM-B, purchase 10/2, and tape/paint black the ends of the white wire to mark them as current-carrying. (To avoid the re-marking, they make red/black 10/2. Purchase this at an electrical supply house, since you probably won't find at a big box store.)

None of the distances listed will cause a problem with voltage drops. However, you didn't list the distance between your main panel and the subpanel.

In my mind, you'll need at least 100A service to this subpanel. The reason is that it sounds fairly likely that the AC, the lift and the compressor will need to run at the same time. It might be possible to get away with 75A, but you're probably heading for a lot of nuisance trips. Not only will that require a visit to the main panel in the house, but you'll be left in the dark while removing that coil spring.

"In my mind, you'll need at least 100A service to this subpanel. The reason is that it sounds fairly likely that the AC, the lift and the compressor will need to run at the same time. It might be possible to get away with 75A, but you're probably heading for a lot of nuisance trips. Not only will that require a visit to the main panel in the house, but you'll be left in the dark while removing that coil spring."
That was my exact thought. It would be approximately 20' of cable to run out of the house, down the conduit, under the concrete breezeway, and back up inside of the cinderblock wall, where it will exit below the sub panel.

Another issue I have, is where and how to put the grounding rods. Everything is concrete. The closest non-concrete area is 20' across the garage on the far side of the building. I guess I have to drill holes in the sidewalk/breezeway concrete and drop the spikes down. Not sure how to sink them though. Maybe a sledge on a ladder, or a picket pounder if I can find one.

I'm trying to get a copy of the NEC from the library. Is there an easy "how-to" on doing a load calculation for the main box. Someone on another site suggested it. I did a google search and found an automated one.

Also, my gang boxes have 1/2" punchouts. All my conduit is 3/4". I tried to get the gangable boxes with 3/4" punch outs and the depot doesn't carry them. Can I grind out one of the 1/2" punchouts to 3/4" or is there some code restriction on this.

Last question is kind of stupid, but again, I appreciate the help.

if you need to drive a ground rod, an attachment is made for hammer drills that goes over the end of a ground rod and drives it in with the drill set to hammer only. i dont know what this costs.

another way is to drill your hole and fill with water and work the rod up and down. push down fast and hard and pull up slightly and repeat. the rod will go down surprisingly easy. when there is about two feet left, you can drive it with a sledge.

as for the boxes, you can drill out the knockouts. no problem with code. a uni-bit works well. if you dont have one, or dont think you have any other use for one in the future, it may be more cost effective to return the boxes you have and get the 3/4" ones from an electrical supply.