Light: "Full sun" is generally understood as being at least six hours of sun a day, something you're likely to experience in a garden that faces mostly due south or southeast. Most flowers and vegetables need at least that much sun a day in order to grow properly. Some, such as peppers and tomatoes, prefer even more. Others, such as lettuce and dogwood trees, do better with less.
This definition--and other terms such as "partial sun" and "partial shade"--also depend on latitude and climate. Full sun in Texas is a lot more brutal than full sun in Montana, especially during the summer. Tomatoes in Texas may scorch after six hours of sun, while the same tomatoes in Montana may need at least 8 to 10 hours of sun. If you're growing something for the first time and you're not sure how to interpret such terms in your area, use your own best judgment or consult your local extension agent or nursery experts.
Soil
"'Average soil'--there's a phrase that leaves me completely in the dark," says James. "It's downright undefinable, and I have no idea what it's supposed to mean. 'Average soil' is taken to mean something in between pure clay and pure sand. That's great if that's the kind of soil that everyone has, but it's not, which means there's no such thing as average soil." There are an infinite variety of soil types across the country--sandy loam, silty clay, pure clay. If your lot has been regraded, you may actually be trying to garden on fill dirt.
"What the instructions should call for is 'improved soil'," says James. "No matter what shape your soil is in, chances are there's room for improvement."
Spacing