The first thing to do is figure out how ants are entering your home. Observe the ants and their trailing pattern, and seal areas where they are entering the structure. Caulk and weather stripping are useful tools when creating an impenetrable barrier.
When ants enter a home, they are looking for one of three things; Food, water and/or shelter. Keep all food items in stored air-tight containers to prevent pest entry. Make sure to keep counter-tops and sink basins wiped dry to eliminate standing water sources. Seal entry points such as wire and plumbing penetrations, cracks in the foundation and around window/door casings.
Inside your home, use caulk to seal cracks and crevices around countertops, sink basins, pipe access areas and wall/floor junctions. This creates a permanent barrier to help keep ants out.