It isn't hard to prune apple and plum trees, especially after the trees have been established. It's all about population control so the trees aren't too crowded. They must be carefully pruned carefully in their first few years so they will be on their way to looking and maturing as desired. Pruning also is important as the apple and plum trees expand out of the garden so that the tree doesn't dominate the gardening space.
Prune your apple or plum tree in the spring. Plums grow with a main stem of about 4 feet long; this is before the branch system starts to expand outward.
Find where the branch attaches to the trunk of the tree. There will be a groove on the top part of the branch. Imagine a line traveling diagonally from that part of the branch downward and away from the trunk. Cut along that line with hand prunes or pole prunes. With small branches, squeeze the hand prunes on the imaginary line to snap the branch. With larger or higher branches, wrap the pole prune around the branch and saw up and down until the branch detaches.
Focus on having the center of the tree open. The main branch system will then form up on the outside, so that the young wood will grow up inside the interior of the tree. This is how you can create the half-standard tree and if you are growing plum or apple trees.
Decide on which branch is the lowest one and then prune it about 9 to 12 inches above the bud. This pruning will determine where the buds will grow from, leaving only the best of them. They will, due to your pruning, be at a wide angle, as opposed to the stem.
Cut the other shoots, picking only the best five to leave. These will determine your branch system's main growth. This method of pruning will cause the very top bud to grow the strongest, but you will want more buds to grow on the lower branches, so you can use a knife to barely cut below this main bud. This tiny cut will force the lower buds to produce more heavily. When pruning, you can make the branches angle out wider by selecting which buds you want the branches to come out and make small notches in the tree bark above these buds.
Prune your tree in an outward-pointing direction for the first couple of years. You will have removed about 1/3 to 1/2 of the new wood. Later on you will just barely top what you want taken off and still later you won't have to cut into the tree at all. Now, your plum tree should have about seven well-spaced branches that form the main branch system of your tree. These main branches will have smaller, lateral growth branches that will be the true form of your tree's wood.