Lay your pet on its side and place yourself behind it. Place your palms one on top of the other and place them above the higher part of your pet's ribs. Give 100 compressions a minute. If your pet is very small then just use your fingers.
Mouth to mouth
Breathe into your pet's mouth in order to get air into their lungs. Keep an eye on their stomach to ensure it's filling up at the moment you breathe out.