I am going to develop some styles for our institution in the upcoming weeks. Before I start I was thinking about how others create new styles. Do you usually modify existing styles, or do you usually start from scratch? Do you have like a repertoire of macros that you use to build the styles?
In theory modifying existing styles sounds easier, but I have the impression that this can quickly turn out to be more complicated.
Depends on the style. For most purposes, starting from existing styles is orders of magnitude faster. If you want to build something very complex, starting from scratch might be better.
In the very rare instances when I do that, I first spend some time thinking about the structure of the style. There are very few macros I recycle for those cases.