Thankyou to those who have replied, the answers have been extremely helpful. However after viewing the articles, i have some more questions.

1) What is a 'leader'? I have the impression it is the branch that grows up out of the chopped off trunk, rather than straight out like the others.

This leads to my second question.

2) If, as Brent Walston says in his article 'Developing Large Trunks for Bonsai', it is best to grow a tree for 10 years or so before chopping its trunk and moving it to a Bonsai pot, won't this result in just a large trunk with a small branch growing out the top, i.e out of proportion, a tree that bears no resemblance to itself in the wild? To have an idea of what i mean, check out the picture of his chopped Zelkova in training.

3) Is it also true that a tree's trunk will thicken very little in a Bonsai pot? If this is true, than as a beginner I have wasted a lot of my time as a lot of my young trees and cuttings are in Bonsai pots already.

Any replies would be gratefully appreciated.

Bren.