The best place to place mouse traps is where the mice are hanging out.
For example if the mice are running around on your counter then place mouse traps on your counter to catch the mice.
Also place mouse traps on the floor near your stove, counter, inside kitchen cabinets if your mouse is getting into the kitchen cabinets somehow.
I also recommend placing mouse traps around your house outside where you notice mice are coming in.
It's best to get the mouse trapped before it is able to enter your home.
Mouse traps can be reused multiple times to catch multiple mice.
If you have the wood snap mouse traps or other snap mouse traps they can be reused multiple times until you catch all the mice or until the mouse trap breaks.
I have several of the wood mouse traps that I've used for 10 years now catching mice over and over when they are active and come into my house.
I also set mouse traps outside around the house where the mice may come into the house.
Sometimes the mice get trapped and killed before they are able to enter the house which is a good thing.
To keep mice out of your house make sure to clean up debris around your house and seal up any holes with some wire that the mice cannot get through so easily.