I'm up in zone six.

While this year it's not going to happen, I'm planning on getting a
vegetable garden set up for next year. The backyard is shaded with a
couple of large trees, and I know I have a back-breaking amount of of
digging to do to get the rocks out of the ground (Damned New England
earth!), but what else can I do to make sure it's ready to be planted
come spring 2011?

The soil's a heavy clay and the water table is all of two feet
underground according to a perk test done in 2007.

Thanks!