Amend the soil w/ 1 bag of organic material (leaf mold or peat moss). The hole should be 2-3 times wider than root ball. Tree should be planted slightly higher than surrounding grade level. You may need to remove some of the soil at the top of the root ball or container to expose the flare of the trunk. The flare should be above ground leve. The hole should not be any deeper than the root ball; you don't want the tree to settle and become oversaturated when it rains.

I wouldn't recommend fertilizer but you may want to get some "root starter" in water to pour into the hole before installing the tree in the hole. If there's burlap on the ball, but it back to a couple inches below ground level. If it's left exposed it can wick moisture out of the hole. Don't overwater the tree when you plant it. 2-3 GPM sounds like too much and too fast; you don't want the ground to become soggy from watering. I'd water the tree slowly once a week when the weather has been dry or very hot, during the first summer. Weekly water will encourage the tree to seek out from deeper sources.

Cover the ground with 2 inches of mulch, preferably leaf mulch or shredded hardwood. Do not put it on too thick or create a "mulch volcano" which you often see around the trees near shopping mall parking lots. Keep the mulch pulled back a couple inches from the trunk--otherwise you may have problems with voles devouring the roots. Mulch should extend out to cover the entire soil area that you amended and be kept free of grass/weeks that will compete with the tree for moisture and nutrients.

Staking is discouraged unless the tree is in a particularly windy spot. If required the tie should positioned to allow some flexing by the tree which will encourage the tree to strenthen its own root system. Stake should not stay on more than one year.

Filbert

Most sources don't recommend amending the soil around plants such as trees. If you have one doing well in that site already, then that's evidence it likes your conditions. However, if you are dealing with the hardpan left by new construction techniques, I would be tempted to amend- that soil is awful, and definitely not "native". If you do anything in clay soil like that, don't plant too deep.