Tree pruning is both an art and a science. It is worth taking time to learn about different pruning cuts and methods to ensure the best possible outcome for the health of the tree you are pruning.
Cuts to avoid
First, there are cuts to avoid. In general, avoid topping and heading cuts as these types of cuts result in little to no healing, future decay, and many weakly attached sprouts around the area of the cut. Heading or topping cuts are cuts made in the middle of a branch where there is little opportunity for healing to occur.
Heading cuts may be required in extreme cases such as when there is an ice storm or storm damage, but otherwise are not recommended.
Proper pruning cuts
Good pruning cuts are made just outside the branch collar region. The branch collar is the area of swelling where a branch attaches to the tree trunk. The branch collar region is rich in energy reserves and defensive compounds that hinder decay. Good pruning cuts avoid cutting into the branch collar so that the tree will have the best opportunity to fully heal and avoid decay.
Fully healed: The pruning cut below that was made just outside the branch collar has completely healed over. Trees are quite capable of healing pruning wounds when pruned correctly.
Reduction cuts are another type of pruning cut that can reduce tree height or size and are better for the tree over the long term if removing a larger branch is required. The idea with a reduction cut is to prune the branch back to a side or lateral branch that is at least 1/3 the size of the branch being removed. Pruning back to a lateral branch results in less resprouting and helps redirects tree energy into the lateral side branch that remains
For even more information on pruning you can watch this K-State Garden Hour Presentation: