Every time you add something to your scene in Blender, give it a name that makes sense. It's a very disorienting feeling when you open a .blend file that you haven't worked on in a while and you see that your characters are Cube.001, Cube.012, and Sphere.007, and that really cool skin material you made is called Material.015.
On small, one-shot projects, ambiguous names may not be so bad, but properly naming material makes finding it later that much easier. And on larger projects, good organization is even more valuable. Not only is it smart to name everything in your .blend file, but it's also a good idea to have a good structure for your projects. For most of my projects, I have a separate directory for the project. Within that directory, I create subdirectories for my libraries of models, materials, textures, and finished renders. For animations, my renders directory is broken down even farther into each shot.