Pictures will help.
Progressively prune them, not all at once. You don't want to take off too much at once that causes a crazy suckering response. This may take a couple of years of pruning to work into a good shape. You don't want to sunscald the tree either, by exposing shaded areas to intense sun suddenly.
In part, the end result will be based on the structure that was established by early pruning/ or the shape that occurred from a lack of early pruning.
I've found that the State Extension service has some easy instructions to start to get the ideas of apple tree pruning.
As with all types of fruit trees, get an understanding of where the fruit grows, and on what age of wood. Some like to produce on one-year-old wood, some on two.
Start with the easy to get at damaged and deadwood, keeping in mind if you will be going for an open-vase shape or central leader based on the established structure. Open-vase is popular with apples to provide sunlight penetration, have an easy to work shape, and good air circulation to keep fungal problems reduced. Removing leaf litter from the ground is suggested if there is a fungal problem, thereby reducing spores in the area.
Reduce the watersprouts partially so provide shade, so the bark can toughen-up.
Look for weak crotches (lots of fruit weight can break them) and rubbing limbs. Someone suggested grafting branches between trunks that are leaning away from each other as a natural cable. An interesting idea. So often you will find included-bark crotches if they weren't pruned and trained early.
You will want to have "ladder bunks" (as I have heard them called), openings to get your orchard ladder into the tree and have room to work, both for pruning and harvesting.
Most people prune in late winter (depending on climate)/ early spring. In PNW where its mild in the winter, usually after a hard cold spell is acceptable.
Some people will prune growing (not mature yet) trees in the summer to keep the size down.
Pruning watersprouts is generally accepted year-round. It is easier to clip them when they are small.
Often there are old stubs that have water sprouts coming out like crazy. Nipping these watersprouts doesn't seem to take care of the problem, as the stub will continue to re-sprout.
Aiming to keep more of the branches that are less the 45 degrees above horizontal, and removing/ reducing those that are more than 45 degrees above horizontal is a decent rule of thumb.
Aim for more thinning cuts than heading cuts.
If I am after a well overgrown tree, I'll often stub off a bunch of stuff with a top-handle saw (compact), then figure out where the end cuts will be as the tree shapes up. I'll do the finish pruning cuts in the end, so that I don't spend the time doing a number of proper pruning cuts, then prune out the entire limb because I'll decide it should go in the end. Loppers achieve this intermediate step pretty well, too. I'll usually have large loppers, small loppers, hand pruners, a handsaw, and a top-handle saw as my cutting tools. An orchard ladder is fantastic.
Mulch and water during the growing season seems to help ours develop and hold the fruit on the tree longer into the season.
Again, a multi-year process.
There is lot of good info out there that will be more well-assembled that what is above, and will have diagrams and pictures.
http://s658.photobucket.com/home/southsoundtree/index
This is my photobucket album. I think that the "Keating apple" pics are on the second and third pages. There are some before, during, and after shots of a couple of neglected apples that had their first pruning in a while. Some of the large branches were broken, so more was pruned off than I might otherwise had done in one shot. I think that I did a good job on them, whether or not it will show much in these pictures. Over time the underdeveloped half of the tree (was shaded out by a large maple limb that the homeowner removed, resulting in some of the large top limbs being broken, and subsequently removed).
Oh, here's a link:
http://ir.library.oregonstate.edu/jspui/...edAppleTree.pdf
