Pruning is as much of an art as it is a science.
First lets talk about what shouldn't be pruned in late winter. Stay away from maples and pines, when cut they will bleed sap.
But dead wood should be removed from any tree or shrub including maples and pines. Dead wood is a way for pest and disease to enter the plant.
I use three main tools; hand bypass pruners, loppers and a pruning saw. All should be sharp to make the best cuts.
The right tool for the right cut is important. For small branches it's the hand pruners, a little bigger, the loppers and for even bigger the saw.
The trick is what to cut and what to leave. That calls for close study of the plant, studying pruning diagrams and most of all talking to people who prune for a living. Most garden centers offer a pruning class.
The best thing I did to learn about pruning was talk to Reed Soergel at Soergel's Orchards. He was able to show me what I needed to know in 10 minutes, solving a mystery which plagued me for over 10 years. They offer an annual free pruning class which is filled with important information. This year's class in March 2, 2013 at 1pm. Be sure to call and register 724-935-1743.
When you decide what needs to be pruned, make the cut and then step back and study the plant again. The worst mistake people make is to jump in, start cutting everything and then step back to a nightmare worse than a bad haircut.
For large limbs, make two cuts. The first is 12 inches from the trunk, the second leaves a nub of about a quarter inch. If the prune is made with just one cut close to the trunk, you risk tearing bark off as the limb falls.
I produced a Digging with Doug video about pruning, it's in the upper right hand corner of this blog page. Take a look, it will help.
I've also included an illustration below for a better understanding of basic pruning.