Surveillance should be the first step in geting rid of mice and rats both inside and outside of your home. Indoors, check your cabinets, pantry or any other areas where food is stored. There are some telltale signs that indicate whether critters are getting in. For example, look for chewed-up paper and disturbed or torn-open food containers. Most importantly, scan for what looks like tiny brown or black seeds or raisins. These are rodent droppings. You may also notice a sweet scent, which is probably rodent urine. Also, don't forget to check your attic, basement or crawlspace areas for these signs. Check for any openings that lead outside.
Outdoors, check for holes and cracks in exterior walls or the foundation. They don't have to be large openings; rats and mice can fit into holes from 1/4" to1/2" in size. Rodents often get in where pipes or other man-made openings for utility lines enter the house. Check exterior doors and windows to make sure there isn't enough room at the bottom of the door for a rodent to squeeze under or that window screens aren't loose. Use a ladder to look at your roof, around the chimney (also check in the chimney) and the roofline, as well as attic vents.
Familiarize yourself with basic ladder safety procedures and follow them to avoid serious injury from a fall. See the project, “Ladder Safety” for more detailed information. Invest in an adjustable ladder stabilizer that attaches to ladders and braces onto the roof.