CPR involves three basic steps: A) ensuring an open airway, B) providing rescue breathing, and C) performing chest compressions if there is no pulse. For step A, check that the animal's airway is clear of any obstructions and the head is extended. For step B, give 3-5 breaths for small animals and 10-12 for large animals or until the animal starts breathing on its own. For step C, compress the chest at a rate of 120-150 times per minute for small animals or 80-120 times per minute for large dogs. Continue CPR until the animal has a pulse or breathing, or you become too exhausted to continue.