In general, Magnolias are rather acid loving and prefer a reasonably fertile, loamy and moist soil that drains well. Pick a site that shelters the Magnolia from North and East winds. For the first few years, stake young Magnolia plants and top dress liberally, each April with leaf mold, peat or compost.
Since magnolias are somewhat difficult to transplant, move in the Spring. Dependent on your zone, this would be either March or April and with a ball of soil still intact within the root system.
Pruning is not generally necessary unless a M. grandiflora is being trained against a wall. Then remove forward facing shoots from the base in April.