Keeping the area open to air and light helps the process. The most important part is proper pruning cuts. Don't leave stubs. The branch collar is somewhat the shape of an old horse collar, and it's vital to the health of the tree that this be left intact. Older methods of pruning used to recommend sawing branches off totally flat against trunks, but the newer ideas indicate leaving the branch collar intact.
Many books have excellent photos of proper pruning techniques.
This book would make a great holiday present for anyone interested in learning more about pruning techniques.