We have poorly draining areas in our garden, so we've raised beds at least 8 inches above grade. The ideal soil for your vegetable plot would be a slightly acidic sandy loam with ample organic matter. When I make a new bed, I use a mix of equal parts of soil, sand and organic matter. This would help ensure good drainage throughout the bed. Many gardeners also incorporate a slow-release fertilizer into the soil at the rate of 2 to 3 pounds per 100 square feet.
Variety is crucial, too.
Brave souls plant tomato plants in late July for a fall harvest. But most of us set out transplants in March and enjoy tomatoes in late May and June. I have several large ones and do not have a greenhouse. However, our sun is so hot that even New Guineas appreciate some shade. There's no guarantee New Guineas will pull through winter.