A properly pruned tree produces better fruit and is easier to manage because it is kept to a manageable size. There are lots of things one can learn about pruning and lots of resources available to learn from. The topic is too big to tackle here, but I'll mention a few of the key points…

Our favorite resource is The Backyard Orchard, which has the definitive page on Pruning and Training.

Keep your tools sharp. Bypass pruners (hand size), bypass loppers (same thing only bigger), and a small saw will generally be sufficient for most pruning jobs.

Some types of trees should NOT be trimmed in the winter. These include citrus and avocados, which should be pruned very little, and not when there is a chance of frost. Apricots and cherries should be pruned in the summer, after the fruit is picked, when there is minimal chance of rain. They are both susceptible to fungal infections when pruned in the wet season.

Stone fruits (peaches, nectarines, plums, apricots, pluots) and pome fruits (apples and pears) should be pruned when dormant, mid-December to mid-February in Santa Clara Valley.

You should know what shape you are aiming for when pruning. In The Orchard, we are using an open center approach for almost all of the trees (see an excellent description in UC's publication on Training and Pruning Deciduous Fruit Trees). In this approach, the trunk of the tree is only 2 feet tall. Yes, we cut each tree to a 2-foot stick when we planted them. In the first year, we develop 3–4 scaffold branches off that trunk. The scaffold branches spread at a 45-degree angle upward and outward. Smaller branches and fruiting branches grow from the scaffolds. The resulting tree looks like a martini glass, with branches around the outside and empty space inside. No branches are allowed to grow in the center. This allows sunlight and air circulation throughout the tree, which in turn encourages the best quality fruit. We limit the trees to about 8 feet tall, pruning both winter and summer to keep the tree under control. This way, we can reach all parts of the tree from the ground, to pick, prune, spray, and cover with nets if necessary.  The pictures in this post are our Elberta peach (above) and Moorpark apricot (below), pruned to an open center system.

You need to know where to cut to have the effect you are looking for (more details in the Colorado Extension on Pruning Cuts). Cutting off a branch all the way back to its parent branch is called a thinning cut, which thins out the tree for light and air circulation. Cutting a branch back to a smaller side branch is called a reduction cut. This shortens the branch and directs growth to the side branch. A heading cut shortens a branch to a bud and encourages new growth near the point of the cut. This is good for shortening a fruiting branch, leaving a short, strong branch to hold the fruit rather than a long spindly branch.

It is important to know where the tree will produce fruit (see Table 1 here). Some produce fruit on the new growth as it comes out (mulberries and persimmons), some produce fruit on last year's branches (peaches and nectarines), some on older branches (apricots and plums), some on long lasting spurs that are at least two years old (cherries and pomes). If you cut off all the fruiting branches you won't have any fruit!

With all that in mind, start pruning! First, remove any dead or diseased branches. Then remove growth in the center to restore the “open center”. Next prune each scaffold branch, ideally allowing it to become two branches a couple of feet from the trunk, and each of those to become two more a couple of feet further out. The tree never cooperates perfectly, but this is the idea we're going for. Save enough small lateral branches on each scaffold to host the fruit. Make sure you know what those fruiting branches look like for each type of tree!

One final recommendation: brush up on pruning before you start. Every year I read a couple of good web pages and watch a few videos. Look for information from the universities where the fruit grows best. Look for peach info from U. of Georgia, apple info from Washington State, cherry info from Michigan State. California, of course, excels in all types of fruit, so the U. of California information covers them all.

I assisted Allen Buchinski in a great pruning video with pictures from The Orchard (on Zoom in the pandemic year of 2021). Allen pointed me to a very effective series of 4 peach pruning videos gathered together on the Master Gardeners of Santa Clara County site.