Mistake: No transition from dense to sparse
The biggest challenge for those who are new to texture is breaking away from using lines to enclose and outline their textural forms.
It's important to realize that lines don't actually exist - they're a tool we employ, and they are very effective at demonstrating the borders between the volumes of our forms. They work very well when dealing with general construction, but once we get into situations where we have a lot of tiny forms that run along the surface of our major constructed forms, this tool becomes much less effective. It can quickly result in a lot of lines crammed close together, creating high contrast, visually noisy areas that turn into unintended focal points that draw the viewer's eye. Of course, we've discussed this previously - the solution is to rely on cast shadows instead.
This doesn't mean drawing in our textural forms with line first, then applying shadows. It means relying purely on shadows only, and allowing there to be edges that get lost and found throughout our texture. This happens because the shadows where two forms meet (like two scales coming together) will generally be much deeper, since light has more difficulty penetrating these crevasses. As the amount of light increases, the shadows on external edges will disappear much sooner than those in these deeper cracks, causing those edges to get "lost" and then be "found" once again.
This is extremely useful, because it allows us to punch gaps in our textures, providing a means to transition from densely packed areas of black ink, to areas that are mostly just left blank.
Additionally, using this approach allows us to imply a lot more information without actually having to draw it all. As we move further to the right side where the texture is left sparse, the viewer's brain will fill in most of the detail there. If instead we were to outline everything in its entirety, we'd be telling the viewer that every single piece of information that has been drawn exists, and that there is nothing that exists that has not been drawn. There is no room left for implied detail - everything is instead entirely explicit. That is an inflexible way of working, and should be avoided.