Sunlight is free, and "it's my priority for production," says Sal Gilbertie, co-author of "Small-Plot, High-Yield Gardening" and chairman of Gilbertie's Herb Gardens.
A high-yield garden needs direct sun "a minimum of eight hours a day," or two-thirds of the day, Gilbertie says.
Some believe that you can get away with a little less.
You want at least six hours a day, says P. Allen Smith, host of P. Allen Smith Gardens and author of "Seasonal Recipes from the Garden." But it must be direct sunlight, not half-shade, he says.
Pick up a handful of soil and squeeze it. "It should fall apart when you let go of it, not stick together," Gilbertie says. That way the roots can grow unhindered.
"If it's a new bed or new containers, then you want to get a soil that's rich in compost," Gilbertie says. If you need it, you can buy "all sorts of prepared compost" in bags to supplement your soil.
Another important point for in-ground gardeners: Since you're eating what you grow, make sure the area you're using hasn't been previously contaminated with anything that could be harmful.