Photos should be taken from the eye level of the animal, not looking down on them from above. A good sign that you’ve got the right angle is when you can see their chin. The very best photos are taken when the animal is seated; they’re more upright that way, just as a person would be in a portrait.
A head-on view, or slightly turned view of the animal work great. Imagine you’re taking a school photo! Don’t get so close to the animal that the nose looks larger in the photo than it actually is.
High resolution images taken in good light will help me see all the details. Try to take photos outside on a cloudy day, or in a room with lots of natural light.
If the animal has passed away, I will use whatever photos you have and still make a lovely portrait …. maybe with a little more guidance from you.