Pruning in the winter is a great way to spur new growth and set your trees and shrubs up for success in the Spring.
One of the benefits of pruning in the winter is that you can see what needs to be removed and what should be left. That is, at least, the case with deciduous trees. Another benefit is that the plants are dormant and won't object if you work on them a little.
In order to eliminate competing branches from ornamental trees, they should be pruned. Weeping Cherries, Flowering Dogwoods, Flowering Crabapples, and other similar plants have a proclivity for sending branches in a variety of directions. It is your responsibility to determine how you want the plant to appear and then begin pruning to attain that appearance.
But first, poke your head inside the tree to see what you can delete. This is similar to peeking under the hood, and you'll notice a lot of small branches that have been deprived of light and don't contribute anything to the plant. They are merely present and should be removed.
Any branch that grows toward the core of the tree and receives little sunlight should be removed. When two branches cross, one of them should be deleted. After you've cleaned up the guts of the plant, you can begin shaping the outside.
It's actually fairly simple to shape the outside. Simply visualize how you want the plant to look and draw imaginary lines to represent the plant's finished form. Anything outside of these imaginary lines should be cut out. Cutting the tips of branches that have not yet reached these imaginary lines is also necessary to force the plant to expand out.
Plants have two types of growth: terminal branches and lateral branches, for the most part. Each branch has a single terminal bud at the end and numerous lateral branches on the sides. The terminal buds grow away from the plant in an outward direction. If they aren't clipped, they will continue to grow in the same direction, making the plant tall and thin. That is why the trees in the forests are so frail and unappealing.
When you cut a plant's limb, the plant produces new buds directly below the wound. When the terminal bud is removed, the plant will produce many buds; this is how you get a good, full plant. Don't be frightened to prune your plants; they'll look lot better as a result. They become fuller the more you cut them.
This is something that a lot of people have a hard time with. They can't seem to get themselves to prune. Particularly with plants such as Japanese Red Maples. Even the thought of trimming a plant like this kills them. Just go for it! As a result, you'll have a lovely plant.
Examine the plant with a critical eye. If you notice a branch that appears to be growing in the wrong direction, cut it. It will grow back if you make a mistake. The only error you can make is not pruning. I hope this is helpful and does not get you in trouble with your partner. Pruning has been the source of many a family conflict.