Answer: Winter, when apple trees are fully dormant, is the best time to prune. Fruit tree pruning is partly art and partly science. There are different types of pruning depending on the needs of the tree and the desires of the grower. For an introduction to it, including helpful photographs and diagrams, you might take a look at the following web site: http://www.ces.ncsu.edu/depts/hort/hil/ag29.html You might also want to take a look at a book or two about pruning.
Q&A Library Searching Tips