Remember the 4 D’s.
The first thing to do when pruning a fruit tree is to remove Dead, Disease, Damaged, and Deranged branches. Deranged meaning branches which are sticking into other branches at strange angles or that could possibly rub the bark off of another branch. Check out this resource from Oregon State University for a really good write-up about this whole process: Know your tree type
Dwarf fruit trees for example benefit from slightly different pruning techniques than nondwarfs which can grow up to 40 feet tall. Keep structural branches intact and prune for the right ‘shape’.
Different types of fruit trees benefit from different overall shapes. For example, a vase shape is often used for stone fruits like Peaches; while a central-leader shape is often used for Apples and Pears. Check out the link above for photos. Did you know?
Most fruit trees we plant have grafted unions between two different trees. The top is a fruit bearing variety, bred for tasty or productive fruit, and is often joined together with a different variety used as a “rootstock”. The rootstock is often a variety bred for disease resistance or to confer some other benefit. | 
