I have two things to focus on: the trench, and the garage itself.
Know your local conditions; out here trenchers are not usually effective, due to the large amount of rock. So I use a backhoe or excavator. Our local codes also really like the trench to be 2 ft deep, even for pipe. Finally, our soil is quite corrosive, so oversized PVC is the way we go, sith sched 80 for the parts coming out of the ground.
I said "oversize" conduit because I've seen too many garages, especially detached ones, become either "mother-in-law" apartments, or workshops. The larger pipe lets you pull larger wires later.
In a line manner, work is cheap while the walls are open, and even though the code may not require it, I'd try to place receptacles where the fridge, workbench, air compressor, and table saw are likely to go. You might even go so far as to pipe to a large pull box on the far wall.
