Vegetable patch management
Having good soil is the key to growing healthy vegetables.  This page talks about how to get and maintain good soil

Definition of good soil
Good quality soil is the key to a successful vegetable garden. Ideally it should be high in organic matter with a soft friable texture. When scooped up in your hand it should be crumbly, but when you squeeze it in your hand it ought to hold together in a tight mass. The preferred PH of the soil is neutral to slightly acid.

While the abundance of garden worms is a good sign it is not an absolute indicator as only certain varieties of worms will be present in disturbed soil.

A test I use to see if my garden beds are up to scratch is to push my pointed fingers into the soil at a thirty degree angle. If my fingers slide in easily without crunching the knuckles then I know that the soil is reasonably balanced.

Making and maintaining good soil
Good quality soil does not just happen overnight. In my estimation it takes about three years to bring soil in a vegetable bed up to scratch and then requires further work to maintain it at the right balance. You do not need good soil to start with. In fact you do not need any soil as it is possible to create a good vegetable garden bed on top of concrete. What you have to do though is add the right ingredients to create good soil.

A starting point for what materials to add to a vegetable patch can be found on the Vegetable Patch Design page under the heading Building a Raised Vegetable Patch a  Having built your vegetable bed it's important to add materials to it each time you prepare the bed for a new crop.

Some vegetable gardening books give specific ratios of compost, manure and other materials to be added. However I prefer to go with whatever is available and is the cheapest.