Our dear four-legged friends can be fiendishly difficult to photograph, so if you don't have an existing photograph and therefore need to take a photograph then the following tips should prove helpful:
Try wherever possible to capture your dog outside in natural light or standing by or looking out of a window or in a room flooded with light. Photographs taken indoors completely void of natural light tend not to work well.
Try and always have someone else on hand to help you get the best out of your dog - to hold food and get your dog/s to sit and wait whilst the second person crouches down and takes photographs.
Try to take photograph's reasonably close up and in good focus and try getting different angles; tilting the head up and down or from side to side.
Take as many photo's as you can so that I can understand the character of your dog and his or her movement, markings and texture.