Big thing is not to 'slick" the sides of the hole, or the tree wont root thru the hard pack.
Dig it, then loosen sides with pitchfork.
big hole not recommended anymore, extra nutrients not recommended.
, recommended ! as much as you can, as deep as you can.
If you are in dry country, you can dig out in a 2-3 foot circle, and bury some drip
line, at least 8 inches below surface.
That way you can water tree, and not water surface weeds. should
also consider doing that at distance drip line will eventually be, especially if you are digging in other garden