Take away their food
Rodents will eat anything—to remove rats, you must remove their food source. Common food sources include:
Keep them out of your house
Rats can fit through a space the size of a quarter or smaller. Small openings in homes, buildings, and sheds must be sealed to prevent rodents from entering. Check for openings where pipes or wires enter the building, under eaves, around foundations and crawl space entrances, and near doors and windows. Use cement, 1/4-inch steel hardware cloth (wire mesh), or steel wool and spray foam to seal openings.
Keep them out of your yard
Don’t let your yard be a nesting zone for rodents. Rats will nest in:
You may need to hire a professional if you have a bad infestation. The State of Michigan recommends working with pest management companies who use an "Integrated Pest Management" (IPM). IPM focuses on long-term solutions to pest problems with minimum impact on human health and environment.