Random shading tips
Different world colors for background and reflections
Below is an example of using a different color for the background than for the reflections. In addition to colors, you can of course also use, for example, an HDR image for reflections and radial gradient for camera, or other kind of combinations.
For reflective materials something is needed to be reflected. Common and nice looking method is to use an HDR image. However, sometimes a simple gradient node can look nice in reflections. You can sort of 'paint' your reflections with it in real-time, which is cool :)
Keep the scale
When using procedural shaders, it's important to reset the scale of the object if it has been scaled:
Don't skimp on detail
When modeling an object, it's good to test how the light will bounce off the surface. For example, adding some double-beveling easily leads to nicely highlighted rims for some metallic objects: