Effective rat control begins with prevention. All possible entry points, such as sewers and air vents, should be sealed against rodents. Rats can enter through a hole as small as a quarter (25¢), so even very small holes should be sealed. Rats often enter by climbing trees and coming through broken screens or vents.
In order to address an existing rat population, it is necessary to identify and eliminate their feeding, drinking and dwelling sites. Pet food is an incentive for rodents and should be kept in tightly sealed containers. All human food should be stored likewise. Any standing water or moisture leaks should be addressed. Trash should be disposed of properly, and sanitary conditions should be observed. Wood piles and other rodent shelter sites such overgrown weedy areas should be eliminated.
Various rat traps and possible rodenticides are commercially available. However, because rats tend to avoid unfamiliar objects, it is often necessary to enlist the services of a local pest control professional when attempting to control an existing rat population.