Dig a jagged star or square hole instead of round if your soil is clay. The depth should be only as deep as the root ball and hard and flat on the bottom of the hole. Mix the native soil from the hole with compost to replace around root ball.
Place a 1.5 inch deep layer of just compost over the newly planted root ball and hole and a foot beyond. Mulch well to reduce water needs.
Water well with a hose the day you plant and for several days water every day. Then water every other day for a week or more and then every 2 days for a while. Along with this hose watering, install the drip system focusing on the edge of the outside of the original rootball. Use a 24" probe moisture meter to learn what the soil moisture is doing down lower than your finger can test. We like the one sold by Lincoln Irrigation.
We use irrigation line with an emitter every 6 inches. Water where the roots are today.... near the outside of the root ball and also one foot outside that for where you want the roots to grow - outward. Roots will also grow down. Amend the soil outward from the trunk and add compost and mulch on the top to feed the tree in the future.