When pruning most fruit trees, the gardener's main concern is to create the correct structure to the tree. Apple and pear trees require scaffold limbs (to support the heavy fruiting branches), and peach trees require an open center structure (like an upside-down umbrella). Apricot and plum trees' pruning requirements are simple; this is mainly because the weight of the fruit is not a concern (it is much lighter). Prune in order to remove dead, damaged or diseased branches, control the height of the tree, remove crossover branches, and remove any low branches to maintain the area under the tree.
Cut away any diseased, dead or damaged branches as soon as possible, and remove them completely. Damaged branches can be cut off either entirely, or at their breaking point. (Use your judgment.) Make a clean cut so that the tree will heal properly. This can be done at any time during the year.
Prune your apricot or plum tree when it is dormant (February through March). Determine if you need to cut back any branches to control the height of the tree. You want your tree to be short and wide.
Make your cut in front of a bud to shorten the top branches. This will keep your apricot or plum tree a manageable size.
View the interior of the tree. You are looking for any crossover branches (branches that might rub on each other). Remove these crossover branches.
Locate the branch collar (this is on the underside of the branch where it connects to the trunk) and the branch bark ridge (this is on the topside of the branch where it connects to the trunk) of the branch that you are going to remove. Prune in front of the branch bark ridge and the branch collar; keep the branch bark ridge and the branch collar intact. Do not leave a stub: stubs are entryways for disease.
Inspect the bottom of the tree for branches that are extremely low. You ideally want to have access to the area under the tree, whether it is to mow, mulch, or weed. Remove any low branches by locating the branch collar and the branch bark ridge, and make your cut in front of them.