1. Plant disease or insect resistant cultivars
2. Provide the right amount of moisture
3. Maintain correct fertility levels
4. Rotate vegetables so you don't grow the same or related plant in the same area every year
5. Keep your garden clean (garden debris provides great hiding places for slugs and insects)
6. Time plantings to avoid peak insect infestations
7.  Encourage naturally occurring beneficial insects and other animals
8. Identify the problem - Don't jump to conclusions.  That bug might not be a pest.  It might be a beneficial insect.
9. Determine the problem potential - Sometimes the damage will be minimal. Decide what you and your garden can tolerate.
10. Select the least toxic approach
11. Observe the results of your control method.

Source: Brzozowski, R., and V. Holmes, Smart Gardener, a learning guide for home vegetable growers, UMCE, Bulletin #2282.