I'm beginning to prepare the soil for my vegetable garden. Overall, it's clay-type soil, and I've added some of the leaves from last fall and the grass clippings from last year into the soil and tilled it in.
Should I add any kind of fertilizer or manure? How can I tell what the soil needs for prime growing conditions?
I don't think you can really go wrong with adding manure. Since this is a new garden in clay soil, you'll benefit from adding organic matter (the leaves and grass clippings are a good start), and composted manure will boost your soil fertility.
However, the only real way to know how how much fertilizer you should add is to get your soil tested. Your profile says you live in Utah. This document (pdf) from the Utah State University Cooperative Extension describes how to take a soil sample. It says they charge $10 for a standard test, which is a very reasonable price.
