Once the planting hole is dug, set the tree into the hole and be sure the roots are not bent that might create a girdling root later. Modify the planting hole if needed to accommodate any root that needs more space. If you're planting a budded or grafted fruit tree, be sure that union remains above the soil line. Back fill the hole about ¾ of the way with soil and then water the tree and settle to soil around the roots using the garden hose. Finish filling in the hole and use any soil left over to create a watering berm for the summer.
If you are purchasing a tree already potted by a retail garden center or other outlet, then planting instructions change a little bit. Those trees were potted up and grown last year and have a lot more roots in the container. Some of those roots grew out to the edge of the container and started growing around the pot in a circle. Those will either need to be directed outwards when the tree is planted or if too woody, pruned away.
The planting hole dug should allow the potted tree to rest firmly on the bottom of the hole with the soil in the pot level or slightly above the soil level in the yard. Do not dig the hole too deep and attempt to refill and then pack the soil down so the pot sits correctly. With the hole dug, remove the container and check for those circling roots before going any further. Once those are corrected, and then use your hands to rough the outside of the potted ball, disturbing all the roots on the outside edge. This signals them to grow outward into your soil. From this point the rest of the planting process is the same.
Post planting, monitoring the water that is available to growth is very important, especially so for the pot grown trees. Those soils in the pot are intended to drain quickly and will dry out while the surrounding soil is moist Be sure to check next to the tree trunk to keep the trees well supplied with water.