The planting site should ideally be simply cultivated, do an area as large as possible and no deeper than the tree roots. Adding amendments to the soil is bad, this influences the roots to stay in that area and can start roots growing in a circular pattern.
Planting depth is a common problem with new trees. Look at the base of the tree, if you see a root flair, great, if not carefully dig down to the flair and expose it. If it's more than 4 or 5" below grade you may want to replant the tree at the correct height.
Most people put bark mulch around the tree in a circle about the size of the ball and water right on the trunk. This is wrong.
You want the tree to send roots outward from the base, so make the conditions for roots perfect just outside the exsisting roots. Put down an ideal depth of mulch and water out there. Along with the cultivating of the soil before planting(this soil should not have been amended either), will tell the tree roots to grow out that direction. Don't underwater the planting site, but let it just dry out between waterings. Poke your finger down into the soil to get an idea of how often it needs water.
Nursery trees are heavily fertilized and can go without for now. If you decide to add some more, I like the bagged composted cow manure they sell at garden centers. Just sprinkle it on the surface. Apply some to the surface before laying down the chips, but don't put any on the root ball, there's enough fertilizer there. Follow label directions for rates.
Then finally, talk to your tree, it will like the CO2 you put out and the neighbors will think you are crazy and leave you alone.
