Soil. Till the bed with a garden fork to remove rocks and break up clumps before raking the soil smooth. Then cover the soil with a few inches of compost, till that in, and rake again.
Planting. Start most of the seeds indoors in September―except arugula, which you can sow directly in the ground―then transplant seedlings outdoors six to eight weeks later. (In cold climates, plant in spring.) Always sow extra seeds in case some don't germinate, and keep excess seedlings in case any plants in the ground fail.
Spacing. Though you can follow the recommendations on the seed packets, space seedlings on the tighter end of the range so the beds will look lush.