Pruning tip bearing apples
Most apple trees are spur-bearing but some are tip-bearing. Avoid heading cuts for tip-bearing trees as that cuts off the part that will be fruiting next year. You'll find pages with good pruning instructions on-line for both types of trees. This slide-show on page 10 includes basic diagrams: Growing Fruit Trees Successfully by Oregon State University Extension Service: http://extension.oregonstate.edu/lane/sites/default/files/documents/tree_fruit.tf_specialists.pdf.