Simple things that can sometimes save a culture
Pests are some of the most annoying and difficult problems gardeners face. The best way to deal with them is to keep them out. Regardless of the method of cultivation, pests will infect your garden unless they are not given a chance. Here is a few means of preventing them from entering.
Pets

Pests often enter your crop using pets for transportation. Do not leave your pets in the garden. Their fur also builds up on the sticky buds.
Clothing
Clothing worn outside may contain parasites. Even a single pest can be a vector for a fast growing colony.
Before entering, wash your hands and dress in freshly laundered clothes.
Plant Quarantine
Before letting a plant get into a pest-free garden, quarantine it and use a pesticide or an fungicide spray or dip to make sure.
Planting mix

Make sure the planting mix is composed inert or pasteurized ingredients. If the potting mix is not inert or pasteurized, it can contain pests and disease.
Pest roads and airways
Make sure that all the air entering the garden is filtered. Repair cracks, holes or other open spaces.
Some practical advice that fits in any culture
The greater the insect infestation, the more difficult it is to eradicate it. It is easier to treat a small infection than a large one. The most likely to attack your plants are and detailed preventative and pest control methods to keep them away from plants and eliminate an infestation.
For more information consult The Grower's Guide