Start by identifying the type of ant in your house so you can find out its nesting habits and have a better idea of where they're living (they may be nesting outdoors). Take a close-up photo of the ant and e-mail it (or snail mail it) to your local university extension service (enter your state's name and “university extension service” into any online search engine). The extension service will tell you the type of ant you're dealing with and where it nests. It may give you fact sheets about the ant species and maybe even some advice on getting rid of that particular species. Keep it Clean
A clean house is your first defense against ants. Sweep up food crumbs, wipe up spills, take out the garbage, and don't leave dirty dishes sitting around the house. This takes away the ants' food source. Spray vinegar mixed with water around bowls of pet food to keep ants from feasting there. Erase Their Trails
Where you see one ant, you're bound to see others. That's because ants leave a scented trail that other ants follow. Sweeping or mopping isn't enough to eliminate the scent. Instead, mix one part vinegar with three parts water in a spray bottle, then spray wherever you've seen ants in the past. This will stop outdoor nesting ants that entered the house to forage for food (ants that come inside are not necessarily trying to establish a nest). But vinegar and water won't stop ants that are already nesting indoors. You'll need to kill them with ant bait (see the next step). Wipe Out Colonies
When you see an ant, your first impulse is probably to step on it. But don't. You'll kill it, but for every ant you see, there may be hundreds more hiding in the house. The ones you see are scout ants, foraging for food to take back to the colony. Use these scouts to wipe out the entire colony. Prebait ants in areas you've previously seen them. Ants' tastes change during the year. They usually prefer protein in the spring and sweets or fatty/oily foods in the...