It varies depending on the age and stage of the trees and what you are trying to achieve.
Here are a couple I chopped yesterday. They are both aimed at really small bonsai. This is the first pruning for both.
Trident maple. Blue lines mark long internodes. Because I'm aiming for smaller bonsai long internodes in trunk or branches are not good. Remove all long internodes, even if you want the trunk or branch longer.
Red lines mark long, straight sections. The lower trunk has good bends. Straight sections in the upper trunk would look odd so cut to a side shoot that gives a good bend (and taper)
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Not much left after removing long internodes and straight parts but new buds will grow and give more options for next year.
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These tridents are a year older Previous chops have resulted in some bends and some branches. Remove excess branches so the trunks do not develop inverse taper. Chop again for change of direction and taper in both branches and upper trunks.
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Green arrows show previous chops. Should be able to pick up change of direction and change in taper from previous pruning at those places.
This year's pruning to remove competing branches and apex, leaving better shaped or better positioned. Also remove long internodes, even if the branch/trunk needs to be longer. Much better to take another year than to live with a bare section for ever after.
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Similar process for larger trees but cuts will be proportionally larger and we may be able to tolerate slightly longer internodes in larger sized trees.
At this stage these trees have been pruned once each year. The lower 2 will probably move to 2 or 3 trims per year to encourage more ramification and finer twigs. I'd be happy to spend 6-10 years to get good shohin sized trees from these but you may be satisfied with lesser quality and shorter time frame for your first tree.
