When creating signage for the shelves, I've been through several variations. Again, this is a fluid process because you may think something will work, but then your students don't necessarily like it. Be flexible and willing to change!!
Some people prefer super colorful signage...others keep it simple. My signage for junior high was very colorful, but the vibe and look in my high school library was very sleek and a more professional look, so I kept my signage very simple but clear. Ultimately, I've ended up with the following signage for the ends of my shelves indicating which side of the shelf each category is on.
No matter what signage you choose, talk to the students and teachers to ensure that what you have is clear, and that they understand it. It's all about the end user and you can't be afraid to make changes. Again...be flexible!