Which direction do you clip the coat in?
For most dogs, follow the direction of the hair growth with your clippers. This gives a more natural textured look. Depending on the dog's coat direction, for most dogs that means going from the head towards the tail, down the sides, and down the legs.
For very thick or directional hair that lays flat, such as terrier and wire coats, you can clip in the opposite direction of the hair growth (if going with the direction of the coat isn't giving a smooth or even finish). Reverse the direction, so depending on the direction the coat goes, go up the legs, up the sides, and from tail to head. This results in a smoother, shorter finish with fewer clipper or blade marks to tidy up later.