Plant in sun or partial shade; the further South, the more shade is required. An acid soil, well-drained but moist, suits best.
Dig a hole amply large to accommodate spreading the roots, fill in and firm the soil down well. Water thoroughly and apply a mulch to conserve moisture, particularly the first year.
The two main causes of failure with Flowering Dogwood are very bad drainage and its converse, allowing the plants to dry out. Site preparation or selection will minimize the former problem, while watering freely during periods of drought will keep the plants in good growing condition.
Dogwoods are troubled by borer, and a spray program, as recommended by your county agent, is worthwhile investigating. Apply a balanced fertilizer in the spring, and cut out dead wood after new growth has been made.