Every year for a few weeks we get an ant infestation. They show up suddenly one day and go between the kitchen and bathroom. They go literally an inch away from the cat food every year but never have gotten in it. The bathroom has nothing to eat in it and so really, we have no clue as to what to do differently each year to keep these nasty things from starting in the first place. And like clockwork, a few weeks after they first show up, they suddenly disapear completely for the year.

This year, with Gavin walking I did NOT want then anywhere near the living room, but the path they take goes right by the doorway to the living room and ever year a few make their way into the living room. So, I found that they dislike cinnamon and sprinkled it liberally around the floor and wall where they were coming up. (they are apparently climbing up on the vents - not IN them, just on them) I washed the whole floor with vinegar and water, and was all smug that night because I didn't see any more.
Next morning, they were coming up on the OTHER vent that goes into the kitchen.

At any rate, I wasn't going to sprinkle any more cinnamon around there, as it would likely push them to the bedroom which has carpet, and I do NOT need ants crawling anywhere near me when I'm trying to sleep. To keep them from getting on top of the fridge where a few were trying to go, I sprinkled cinnamon around the edge of the top, and in front of the microwave just for good measure. They really really hate it and WILL avoid areas if they have to cross cinnamon.
If you know where the nest is, I've heard dumping grits on the entrance will get rid of the problem as well.