The best light is outside. However, it is important to avoid the hours when the light is most intense, as too much sunlight will hide some of the details of the coat. Early morning or late afternoon light is ideal! You must be careful not to be in backlight. It is best to put the dog or cat facing the light.
The best thing is for the animal to be sitting. It can look at the lens, but it doesn’t have to. Sometimes a sideways glance offers a natural portrait. To get a good expression you can show it a toy or talk to it. It is important to remember that the eyes are always the first to be seen in a portrait, even if the animal is not looking at the lens.
Concerning the angle of the photo, you should not position yourself too close to the animal, otherwise the photo will be distorted, it is better to zoom in. Be careful! Do not take pictures from above (even if this is how we see the animal most of the time). The portrait will be more natural if it is at the height of the lens. Keep in mind that the final portrait will be hung at human eye level, so the bird’s eye view will no longer be justified and will look strange.
Finally, you can send me several photos (even those that may look bad) and we will make a choice together.