Stay sharp! Good quality pencils will allow the lead to be sharpened regularly. Needle sharp tips on your pencils are perfect for applying detail and getting the precision required to color intricate areas of a design. Thinner points will give you more control over the color produced, big fat rounded ends on your pencils make it difficult to get the brightest colors.
When teaching a class on how to draw animals, we covered mostly graphite and colored pencils, but one of my students wanted to draw with crayons. It was fun cracking open the box of Crayolas and giving the class a demonstration. I shared the illustrations I had done for the book, and we analyzed the characteristics of drawing with crayons.