"Don't hurt your pet, because animals feel pain and sadness just like people." (Sometimes preschoolers are unduly rough with pets because they equate them with toys.)
Verbal disapproval followed by time-out.
Praise your child for playing gently with a pet.
Treat animals gently.
"Pets must be fed or they will starve."
Give an "I" message, such as, "I really feel sorry for Charlie when you don't feed him." In addition, help your child come up with a reminder system, such as a small note on his mirror to help him remember to feed the pet. Sometimes delaying a privilege and linking it with the chore can be helpful (for example, "No dinner for you until Charlie's been fed").
Praise your child for feeding the pet in a timely manner.
Feed your child in a timely manner.