It sounds like you already have a pretty good idea of what to look for when doing this.
Basically I just try and get any of the biggest details that are going to be seen in silhouette. Any "interior" details which will mostly be seen flat-on or surrounded by other, protruding detail, can be optimised down as low as possible and let the normal-map do the work.
Always try to include whatever makes the largest "change in direction" on the surface of a model. Don't have vertices and edges added just for tiny deviations in surface shape, keep that budgetted for the large and curvy shapes which really need it. Zoom out a lot
Obviously you need a decent amount of geometry for deformation around key areas (hips, knees, shoulders, elbows, wrists).
Do you have any examples of your models which you think are either "too low" or "too high"? 14,000 triangles isn't tooooo
bad for a complex model but if you say it's a "simple character", then yeah it should really be less. I'd have to see images to judge and give more focused feedback, since it seems like you already know most of what I've said.