Feed your garden with compost and other organic material, and introduce or buy some worms to help aerate and nourish your soil.
Rather than using chemical sprays, keep pests to a minimum by planting several different species near each other, removing the diseased parts of plants, and picking off pests as you spot them.
You can also make your own natural spray. Try this – combine 4 hot chillies, 4 large onions, 2 bulbs of garlic and 2 litres of water, then cover with soapy water and leave for 24 hours. Now add a little water and start spraying.