Often, the first time someone sees a mouse in their house, they'll momentarily panic — and then they'll calm down and reassure themselves that it's just one mouse. This approach is wise in some ways; panicking won't fix any mouse problem. But, it's also foolish in some ways. Rarely is there just one mouse in the house; you just only happened to see one. So, while it's good to take a deep breath and calm yourself after you see a mouse, you need to follow up that deep breath with some action. Take the following steps to be rid of mice ASAP before the problem gets any worse.
Set a few traps
The $1 mouse traps you can buy at a hardware store will work just fine at this stage. Set up at least four of them. You don't want to risk catching just one mouse and then assuming the problem has passed. You can set cheese in the traps if you wish, but mice are even more attracted by peanut butter. Check the traps daily. If you find a mouse in one, empty that trap, and then reset it. Keep going until you go at least a whole week without catching any mice in a trap.
Clean, clean, clean
Mice can sustain themselves on a surprisingly small amount of food. Even a couple of oats or crumbs spilled in the back of your cupboard is enough to make a mouse say that they like this place. So, get out the vacuum, and start cleaning meticulously. Vacuum out your cupboards along the baseboards, under appliances and furniture, and under floor mats. When you're done vacuuming, wipe all of your surfaces down.
Seal up holes
The mice are getting into your house somehow. You need to carefully look the house over and see where they might be coming in. It could be a hole as small as a dime; small mice can compress themselves very small. You can temporarily plug any holes you discover with some wadded-up steel wool. Mice won't burrow through it. Then, when you get around to it, you can create more permanent patches and solutions.
If you take these three steps as soon as you notice a mouse, you should be able to get rid of any mice before they completely overrun your home. If you are struggling to actually catch any mice or believe their population is growing larger, call a local mice control company ASAP.