The key to planting trees correctly is to not plant them too deep. Planting trees too deeply can lead to problems down the road. This can be avoided by finding the root flare. The root flare is located at the base of the trunk. It is usually buried in excess soil that can be six tor more inches deep. The excess soil is a result of the digging process and weeding at the tree farm. This soil needs to be removed at time of planting.
Dig the hole about two to three feet wider than the root ball. In other words, if the diameter of the root ball that you are planting is 24" across the top, the hole you dig should be at least 48" in diameter. Do not dig the hole to deeply.
Remove wire baskets, burlap, rope or twine. Place the tree in the hole. After exposing the root flare, the top of root ball should be slightly (one to three inches) above ground level.
Use the same soil that came out of the hole as your backfill. Make sure the bottom of the hole is packed tightly with pure soil. Do not add soil conditioners or ammendments. If you are planting in a lawn you can flip over the dug up sod and mix it in with the backfill near the top of the hole.
Do not pile soil on top of the root ball. And definitly do not pile mulch against the trunk. Bring the mulch ring out four feet from the trunk. Do not stake unless absolutely necessary. Unstaked trees develop stronger root systems more quickly.
After the tree has been planted and mulched, water deeply.