The extension of a home's roof over the edge of the wall is called the eave. The soffit is the underside of the eave. Squirrels get inside the eave and can be heard running back and forth on the soffit. This area is usually adjacent to the attic, which they also infest. Unfortunately, squirrels carry disease, chew through live wires and create noise just like rats. To get rid of them, two strategies are fox urine and trap-and-release. Both methods require subsequent repair of holes through which the squirrels got into the attic or soffit.
Buy fox urine at a hunting store. (It is used for smell camouflage.) Wearing rubber gloves to keep the smell off you, soak some cotton balls with the pee. Distribute these around your attic to make the squirrels in the soffits think there's a fox in the attic. Give them a few days to evacuate before you repair any holes they got through in order to infest the house. Even a hole in the soffit to let a pipe through can leave enough of a gap for a squirrel to get in.
Install traps with one-way doors in your attic or hanging from your soffits on the outside. Bait them with orange slices, since the squirrels are attracted to the moisture. Use a large trap so that its tail doesn't get caught in the door, allowing it to escape.
Release the trapped squirrels miles away from your home; otherwise, they will find their way back. Don't be surprised if several squirrels find their way into the cage at the same time. If you don't want to drive for miles to release them into a park, at least walk a zigzag pattern to get to the release site. Otherwise, the squirrels will find their way back to the hole in your soffit.
Another possibility is a strobe light in the attic. A product called Rodent Strobe claims to have success at permanently getting squirrels out of homes.
The urine solution may be only temporary. So jump at the opportunity while they are scared away, and close the holes so the squirrels don't come back and realise there's no fox. The urine comes from the fox fur trade, so you might also not want to subsidise them.