Insect pests affect all forms of agricultural production, from densely planted field crops to high-value nursery plants to grains in storage. A pest management plan should start with foundational knowledge about local pest species and careful planning for pest prevention. We highlighted pest prevention strategies in the first article of this IPM series [http://edn.link/i]. After taking precautionary measures specific to your region and implementing practices that prevent pests from entering or multiplying in your production area, you will need to keep a watchful eye on pest populations and intervene before insect pests are likely to cause too much crop damage, or when they already are causing damage. This article explains some principles and practices for conducting in-field observations (sampling) to inform pest management decisions.