Taking pictures of your pet can be a lesson is patience. Some pets are afraid of the looks of the camera, the sound that it makes, or the flash that may be necessary. I like to use quiet slow movement around the pet so as not to get it too excited, keeping him/her focused on me, and a trust that nothing will hurt them during the photo session. I use an old lens that has 'doggy treat' smell rubbed all over, and I let him check it out - "uhmm must be OK, smells good enough to eat", then introduce the shutter sound slowly, with a reward each time I trip the shutter, we progress with the flash in the same manner. Like I said, it is a lesson in patience.
Before a Pet Photo session, it is most helpful if the pet has a chance to expel any excess energy and excitement through a little exercise, and a chance to get that last nervous potty break in. Below are a couple examples, they were new to the photo experience, but they were eventually happy to smile for the camera. (the Cat is my own 'daughter', she has a lot of experience in front of the lense)