Most fruit trees that die in a warm climate die in their first summer, and almost always for one of two reasons: they were planted too deep, or they were watered on a schedule instead of by need.
Dig wide, not deep
Dig a hole two to three times the width of the pot and no deeper than the root ball. Digging deep and backfilling means the tree settles, the graft union ends up at or below grade, and the trunk sits in wet soil. Set the root ball so its top is an inch above the surrounding grade.
Do not amend the hole
It is tempting to fill the hole with compost. Do not. In sand, a rich pocket surrounded by fast-draining soil holds water like a bathtub and encourages roots to circle inside the amended zone rather than pushing out. Backfill with the soil you dug out. Put the compost on top as mulch, where it belongs.
Mulch wide and keep it off the trunk
Three to four inches of mulch out to the drip line, pulled back a hand's width from the trunk. Mulch against bark invites rot and gives voles somewhere to work.
Water by need, not by calendar
Every day for the first two weeks, every other day for the next month, then taper. Push a finger two inches into the soil at the root ball edge: if it is damp, wait. By the second summer most of these trees need irrigation only in a drought.
Do not fertilise at planting
Wait four to six weeks until you see new growth, then start light. Fertiliser on disturbed roots burns them.