1) Ants often come in for water. If that is the issue, keeping things spotless won't be enough.
2) Cinnamon. Sprinkle it along the windowsills, door frames, where ever you think they are getting into the house. I've found it to work much better than commercial bug killers and it isn't toxic.
When I set out Terro a few months ago it helped me locate two of their entrances. One of them was the smallest hole in between the wood planks against a baseboard. The hole was so small that there would be an ant traffic jam if one was trying to go back in while one was coming out. Little assholes. I would never be able to close up all the entrances they could use if they are that small. The other was a tiny tiny crack in the grout by a base of a doorway. The ant parade is fascinating as much as I hate bugs. At least with the Terro they are in a controlled location and not everywhere.
I also set outdoor Terro baits in the grass around the concrete base of the pool, and close to the areas in the house where I was seeing them inside. I don't know if it helped, but there aren't 100 of them attacking a cracker the second a messy toddler drops one outside.
The first time I used Terro, I was not prepared for how many ants would swarm to the bait. The trail tripled in size once they figured out it was there, but the next morning they were all gone. We live in a condo, so we don't have as much control over the outside, but every time they come in, the terro gets rid of them from our space.