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.
Consistent Pressure Gives a Uniform Look. Keeping a consistent pressure with the crayon on the paper gives a uniform, pleasing look. If you're pressing hard, your hands will get tired quickly, so I prefer to press lightly. Interestingly, being aware of how much pressure you're applying seems to be really hard for younger children. It must be tied to motor skills in some way. It won't hurt anything to tell them this tip, but if they aren't implementing it, just let it go.