Get boric acid. I found mine at a Long's Drugstore. Mix equal parts boric acid and a substance that will appeal to your type of ant. Peanut butter is a good fat, honey is a good sugar. You can combine them by using Cool Whip. Put on a piece of paper and lay out for ants. If you don't want your pets getting at it, I will suggest inverting a colander over it or putting it somewhere where there's no chance they'll get at it.
The next step is crucial: although you will witness a horrific, seething mass of ants all over your bait, resist the urge to kill them. Let them load up on that tasty boric acid and take it back to the nest to destroy all Antkind.
So I've got Deadly Peanut Butter laid out for now. If that doesn't do the trick within a couple of days, it's time to break out the Cool Whip.