Frequency and scrutiny. Frequency tells the tenant it won't be easy to hide new additions. Scrutiny will allow you to remove tenants with a spot or two on the wooden floor before the entire floor is damaged (or entire door, or entire woodwork, etc.). If small problems are addressed, repaired and billed to the tenant, they will be a bit more careful down the road. Sometimes we do have to teach tenants what is acceptable.We have started characterize an additional monthly fee as animal rent. Sounds strange, but we have chosen not to use the word pet but animal. The additional amount for our population is very small but I believe it is effective.