I’m not a good pruning person, but just for starters I’d say that it’s a lot easier to figure out if you start with a youngish tree that hasn’t been overly worked on!
Say you have a one-year old whip that’s about as three or four feet tall. It has one big stem that’s about 1 1/2 inches in diameter, and probably some feathering. That big stem is your central leader. Let it grow a season. Some of the feathers will be getting established, and you want to select about three or four of them which are nicely spaced around and up and down the central stem (think circular staircase here). The bigger the tree is going to be allowed to get the further apart these should be - leave them room to grow. And while they’re very young is the time to train them to a good branch angle.
So now you have a central leader and a lower scaffold. If you cut out the leader you have a vase. But if you leave it you can allow a second set of scaffolds to grow the same as the first. Just leave some space between the lower set and the higher set so light and air can circulate nicely, and so you’ll have some working room. My pear has too many scaffold branches, because I’m greedy and I can’t stand to take them out. You can be smarter than I am, trust me on that!
So that’s what I think is the way to set up a central leader tree, but I’m open to corrections. And I’ll admit that it’s a lot harder to see it on an older tree. But it doesn’t have to be perfect, and that’s a good thing 'cause none of mine are, and I still get more fruit (in a good year) than I know what to do with.
