To slowly develop a nice olive with lots of movement in its branches, you should do cycles of letting it grow out then cut branches short. Generally, unless a specific plan requires something different, it is important to not have any branches that are long and straight.
A mature tree will have branches that are smaller in diameter, and shorter in length that the straight initial distance between the roots and the first branch. Then like a fractal equation, with each re-interation of the calculation the distance gets shorter and shorter.
So use the distance from the nebari (base of trunk, beginning of roots) to the first branch as distance X. Then the first branch have no segment longer than roughly 2/3rds X. the next degree of ramification should have straight branches no longer than 2/3rds of their parent branch's longest straight length X1, and each subsequent degree of ramification the straight distance between branches should get shorter and shorter by a factor of 2/3rds. This is a generic formula, trees in the wild seem to ''generally'' follow this, or at least the human eye seems to see this, and find it attractive. AS ALWAYS, if you have a specific plan that does not follow this, go with your plan. But if you don't know what to do, this generic plan, combined with the fact that the olive tree will not do exactly what you want it to do, will result in an attractive tree. Even using a ''generic'' formula, when done the tree, will almost never look ''formulaic''.
Second trick, at few or no points, should you have more than a trunk and one branch, or a branch forking into 2 branches. Triplets and other arrangements should be reduced to 2, unless a branch is necessary to fill an empty space and there are no buds to potentially replace it. Going through and removing excess branches will really clean up the tree.
Lastly, I would identify the ''main trunk line'', and then remove any branches that are more than 50% of the diameter of the main trunk line. You can let ''sub-trunks'' be larger than 50% of the main trunk, but in general if branches are much greater than 50% the diameter of the main trunk or their origin on the sub-trunk, the tree image becomes more of a ''shrub'' image. Shrubs have branches and trunks of similar diameter. Often a mature bonsai will have none of its original branches that were present when styling was started. Very mature trees will regularly have overly large diameter branches removed to be replaced by younger, less than 50% diameter of the trunk branches.
So following the 3 ''formula guides'' you can train just about any tree. And as always if you have an artistic reason for ignoring these guidelines, you should. But if you do not know what you should do, these guides will help turn out an interesting tree.
Depending on how quickly your olive grows, you may allow it to grow out, then prune more than once a growing season. Let new branches extend, develop at least 6 or more pairs of leaves, let the first couple pairs of leaves harden off. Then go through the tree and prune everything short according to either the formula or your artistic needs. If you want a certain area to not add size, cut back to just past the first pair of leaves. If you want more extension, cut back to 2/3rds of the previous segment. Then when new branches form from the buds will give you a nice zig-zag pattern.
You might be able to cut back 2 or 3 times a year, or as little as once a year. Let the olive tree's actual growth guide how often you prune.
