I have a potted grapefruit tree that I started from a seed about five years ago, so I decided to try on that one. This is about the age that most of the sites I found suggested doing the first training, so I figured I might as well.
It has never been repotted and probably hasn't been watered as well as it should have been. Definitely not fertilized--I don't often use fertilizer.
First I cut off all the dead-wood. There wasn't much, but enough to make it difficult to work with the tree as a whole.
Then I cut the tree down to the point that I could actually work with it before I pulled it out of its pot.
It was seriously root-bound. I'm surprised that the roots weren't coming out of the holes.
It took a lot of work and a water bath to get most of the compacted soil out of the roots. The tap root had twisted itself up in a knot, but I got as close as possible and got it out of there.
I cleaned out the root mass, got rid of the very long, stringy roots, and trimmed the smaller roots inside so that there's room for soil in there.
I mixed the existing soil with composted steer manure (no, it doesn't stink) and put it back in its pot, spreading the roots out over the surface before I put the last third of the dirt back in.
The existing root-mass is smaller than I expected, so I did some more trimming after I had it settled back in its pot. Here's the before and after.
And no, that picture wasn't taken in 2007--I just don't bother to reset the clock on my camera every time I change batteries.
I have an apricot seedling I want to bonsai, but the information I found said it needs to be a minimum of two years old...By that time it will be five feet tall, so I keep looking for other information.