How much do I need to water?

Watering is a balancing act in the first year of any plant's life. One the one hand, newly planted trees whose roots dry out, die very quickly. On the other, watering soil that is already wet causes water logging which is the second most usual reason for plant death in the first year.

When you water, water very well indeed. When you have watered, leave the tree alone until the surface of the soil is dry again. A lot, infrequently is much better than little and often.