Your first battle might be with weeds. These compete with other plants for light, nutrition, and water, so you need to clear them before you start growing. If your plot is small, you can dig the weeds out, making sure you remove the whole plant, plus the root.
However, if your growing area is large, don’t try to clear it all before planting. Hours of digging will only lead to back ache and the depressing sight of weeds returning. And if you resort to a blast of weed killer (glyphosate formulations), you are using toxic chemicals on the very area you want to grow your healthy fruit and veg.
Instead, divide the plot in half. Dig one half, in the other, you will feed the soil by using a thick organic mulch that covers the soil to exclude light. Here's how:
For the mulched half
Cut down the larger weed foliage to just above soil level using a satisfying slash technique (you can use much of the foliage on your new compost heap, so long as there are no seeds). Then cover the area with a mulch that will exclude light. You can use a variety of materials to do this – a layer of compost or well-rotted manure is ideal, recommended 1 wheelbarrow full per 5 sqm, topped by cardboard (weighed down by bricks or another thin layer of compost so it doesn’t blow away), or a black plastic membrane, also pinned down. (Don’t use carpet – many of the dyes have toxic chemicals that can leach into your precious soil.) Leave this for at least 6 - 12 months. It’s that simple. You don’t have to do a thing, as the weeds will weaken in the dark and the earthworms do their work to enrich the soil.
For the other half
Now dig the area where you want to start growing. Take out tough and woody weeds like docks, thistles, nettles, and brambles, removing all the roots. Put the foliage on the compost heap, drown the roots in a bucket of water for a couple of months - then add to the compost heap. See FAQs for how to deal with bindweed or brambles.
Then add compost or manure - one big wheelbarrow, or 5 large buckets, for every 5 square metres of ground. Dig this compost into the top 10 cms of soil, and your bed is ready for planting. If you want to sow seeds, use a rake to break down and gently flatten the topsoil into a fine texture (known as tilth) so the seeds can access soil and water to germinate.