Proper tree species selection is critical before actually planting a tree. Items to consider include:
For what purpose is the tree being planted: Shade; Flowering; Attract birds; Fruit; Screen; Windbreak
What is the planting site like? Will it be close to buildings? Then mature tree height, canopy spread, and root outreach need to be considered. Are there overhead wires? Then a smaller tree will need to be planted or a new site chosen. What are the sunlight conditions? Some trees prefer sun while others will do well in shade.
Will tree be near a road or driveway? Trees near road and driveway intersections may cause a vision issue. Salt from winter deicing if present could affect tree health.
When buying a tree look it over at the nursery to make sure it appears healthy and there are no trunk wounds.
See the links below for more on tree species selection.
Proper tree pruning is another important procedure in the life of a tree. Not all trees will need a lot of pruning but most would benefit from pruning at some point. See the link below for more on tree pruning.