Here is a great instructable on how to plant an apple tree and give it a healthy start.
What you will need:
Plenty of water
Optional: John Deere 2210 w/ Front loader and 3pt tiller
Step 1: Prepare the Area
Measure out your area, and mark the location of where you want your trees.
We plant ours in rows of six. Depending on the type you are planting (dwarf, semi-dwarf, and normal) you will need to use certain spacing. You can look this up on any nursery website.
We are planting semi-dwarf so we need to space the 9 ft apart at a minimum.
When we plant we use the 3pt tiller to till a square patch marking the location of each tree.
Step 2: Dig a Prep Hole
Use the shovel to dig a hole that is about 6 times the diameter of the root ball of the tree, and 4 times as deep.
Set the top soil in a separate pile from the clay that will be deeper.
You can choose to discard the clay or mix it with topsoil/compost to make it break up, and be more futile.
This gives the roots some space to grow.
Step 3: Add Compost/topsoil to the Hole
Mixing the topsoil and compost will provide nutrients for the tree, and an easier medium for the roots to grow out to without becoming root bound in hard clay.
You want to fill in the hole until it is even with the surrounding ground, as the compost will break down over time and cause the ground to sink. It some cases add enough back to keep the root ball 3 inches higher than the surrounding ground.
Step 4: Add the Tree to the Dirt
Position the root ball in the center of the prepped area. Again remember to keep the root ball either even with surrounding ground or up to three inches above the ground to compensate for sinking over time.
Step 5: Complete the Tree Installation
Take the remaining soil, and build it up around the root ball. There should be a raised mound of dirt around the tree trunk with a 3 ft radius, and two inches higher than the top of the root ball.
Pack the soil down with your hands or feet.
Water thoroughly. I usually water with 5 gallons each day through out the fall until the first frost if there is not rain fall.
Step 6: Complete
Continue to inspect your tree for pests, and treat accordingly.
You can also pick up some root stimulant at your local nursery and apply it to help kick start growth.