Nests are usually made of materials like bits of cloth or shredded paper. Or you can check for mouse tracks by dusting suspected areas with a light coating of unscented talcum powder or mason's chalk dust. Wait a day and then shine a flashlight across the area. If you notice small tracks in the powder, then you'll know that mice have been there. Doors and windows should be screened with tight-fitting metal screens.
Trapping is effective, and generally safer than using poison.
Using a spray bottle of disinfectant, thoroughly spray dead rodents, traps, droppings and the areas where you found them. Do not sweep or vacuum mouse droppings in your home until you have wet the affected area with detergent, bleach and water. Dry sweeping or vacuuming might put dust containing viruses into the air. Then place the bag into a second bag, seal and dispose of with the trash. Snap Traps Wood-based snap traps are inexpensive and work well.