Putting in my first organic vegetable garden next year, so forgive me if my
questions are a little naive. I'm trying to get everything tilled up now
and let it rest all winter. I've skimmed several books, one of which
mentioned "Double Digging" tilling. Here's a parphrasing of the process:

Dig a 1 foot trench down the long side of the garden. Keep the top soil in
the garden, but take the rest and throw it in a wheel barrow. After
finishing the trench, go back and dig down another foot of subsoil and put
it in the wheel barrow. (Sounds like a big wheel barrow). Mix the subsoil
with peat moss and compost before putting it back in the garden. Make the
mixture one third peat moss plus two thirds compost, plus one part subsoil.
Rake the top soil back into the trench, then add the new subsoil mix on top.
Dig another 1 foot trench and repeat untill garden is all tilled. Tamp down
when finished. Expect bed to be about three inches higher when finished.
Wait at least a month before planting.

Bascially, I wanted to ask the group if this seems like a sound method. I'm
in western PA and my soil tends to be on the clay side. I don't think I'll
go as deep as two feet, but because the garden area is new, I do plan to go
deeper than one would for standard tilling. In particular, does the mix
sound right? BTW, when they say peat moss, am I to assume they mean peat
hummus? And for compost, I expect to use mostly manure (bags). Is it
reasonable to assume the bed will only be rasied 3 inches?

There is still some grass on the plot I plan to use, and with winter coming
soon, I doubt I'll have time to cover it and kill it with black plastic. If
I just till the grass under, and then cover it and let it sit all winter, I
should be fine, right?

Oh, this might be a dumb question, but... If putting black plastic over
grass for a couple weeks kills the grass, why doesn't the grass die when
covered by snow all winter?