The biggest reason that for young tree failure is because the tree was planted too deep. The hole should be at least twice the width of the root ball. Locate the root flare. The root flare is the spot where the top-most root in the root ball reaches the trunk. This should be just above the soil, once planted. You do not want any soil over the root ball, if there is any scrap it off. Begin filling the hole with backfill soil. Unless the soil very poor, placing amendments is not required.
After you are done planting, apply a thick 3-inch layer of mulch around the tree starting 10 inches from the trunk. Only apply a light layer over the root ball. This helps irrigation to enter the root ball and it keeps the trunk dry. Once completed the mulch should have a 3-foot radius around the tree. The mulch will help defend against weeds and grass. To help your tree establish an extensive root system, a regular watering schedule should be followed up to a year after planting. Research has shown that plants establish quicker with light, frequent irrigation.