I had 15 apple trees when I lived near Ephrata and a guy that had an orchard taught me a few things. Pruning is not too hard to figure out with some basic rules. Opening up the middle of the tree so the light can get in is important. Look for branchs that cross or rub and cut those out. Apples grow on spurs on the branch so when you view the tree, look for the spurs that would produce fruit that would ripen without rubbing on the branches. Otherwise any apples will have bruises etc. Snubbing the branchs at the end causes the branch to get bigger around rather than longer and will support fruit better than long skinny branchs. Size does matter.
A tree that hasn't been pruned in 15 years should be pruned incrementaly over a couple of seasons. It will produce a lot of water sprouts which can be cut as they show up. Also, consider spraying with dormant oil to kill critters that will hatch from eggs laid in the bark. Clean around the base of the tree so mice can't nest at the bottom as they can girdle a tree in a tough winter as they eat the bark when times are tough.
More here:
http://extension.oregonstate.edu/catalog/html/pnw/pnw400/#anchor1107873