Few things provide more fresh tasty produce than a fruit tree. And few things confuse new fruit growers more than pruning.
The task is a simple one that can be done many different ways.
In a commercial orchard, maximum production of saleable fruit is the goal. Things are different in the backyard.
Let's start out with the only thing you can really do wrong, so you won't do it. Apples and pears produce fruit on wood that grew the summer before last or earlier. If you cut all of that off, you won't get any fruit. Peaches and nectarines produce fruit on wood that grew last summer. If you cut all of that off, you won't get any fruit.
The fruit spurs on plums and cherries can be 5-years-old; apples and pears will produce fruit on older spurs too. But the fruit spurs- the size of a bent baby finger must be present if you're going to get a crop.
Now the easy part. Prune the tree to fit your needs. If you don't want to go way up on a ladder, keep the tree short. If you want the tree to be a screen to protect a window, leave on the branches that help it do the task you've chosen. If you want to be able to mow under the tree, cut off lower branches. If you want the grandchildren to be able to pick fruit, leave some low growth
The normal caveats apply to you and the commercial folks. Remove dead or broken wood, cut out crossing branches, and take off those straight, fast growing water sprouts.
In general, you can remove half to two thirds of last year's growth on all trees, and still have plenty of fruiting wood. More thinning will reduce disease, and make bigger fruit. Less will leave a larger crop of smaller fruit. To reduce disease plums and prunes are best pruned during dry weather. Most people could cut off more. Early spring is the best time to prune, but most trees can be cutback anytime- even in mid-summer. One picture is worth more than the 475 words I gave you. The extension service and many online sources have pictures.