AusBonsai

Is there a rule for how a single branch should emerge from a trunk?

Like should it emerge from trunk then go up, down, left then right?

Is my question clear??

No rule as such because it will depend on the style of each individual tree.
Each branch must be in sympathy with every other branch on the same tree. If most all exit horizontal then they all should do so too

On a pine. The Lower branches typically hand down slightly as if weighted bynsnow and as you move up the tree, they exit more upright

Ken

How a branch exits from a trunk depends on the variety of tree and the style of the tree.
Some branches such as on deciduous trees will exit upwards then level out, some as in conifers will exit downwards and some varieties will be level.
The shape and movement of the trunk will also decide on how the branching looks.
Formal trees with straight trunks will have straight branched and informal trunks will have branching that flows with similar movement to the trunks.

I hope that makes sense as there is not one single answer to your question.
Mike