These extra sheet of paper will stop your coloring being affected by the texture of the surface you are working on. Colored pencils will easily pick up even the smallest dents, divots or wood grain textures. For smoother coloring give your page that little extra cushion! It is also useful to add paper between your page and the next when you are using a coloring book, the paper protects the design underneath from being damaged.
Use Crayola. These are the best and have the best color saturation. Use a paper that will grip the color evenly. I like Stonehenge or illustration board. Have a good hand_held sharpener handy. Always try to keep a point on the crayon. This makes it go on more evenly. Apply the crayon in a professional manner. Just like you would any other fine art tool, use control and be deliberate. Don't become five years old again!