While this isn't exactly a 100% guaranteed way to rid yourself of ants forever, it will keep them out for awhile. Just repeat the process every now and again and they'll be out of your hair. :]
*Note: This method is not recommended if you practice Jainism or a similar religion, such as PETA.:]
Step 1: Materials
1) Soapy water (hot water + liquid soap in a spray bottle)
Step 2: Find the Ants
Once you find them, give 'em a blast of that soapy water solution. Don't be afraid about it, really soak the little guys with the stuff. If you see a whole trail of them, go ahead and spray that, too. Spray the whole general area of where they've been.
Why spray soapy water? What'll that do? When ants find something they like, they secrete this weird junk from themselves that the other ants can pick up. The secretion serves as a trail for the ants. But the soapy water gets rid of the trail. Problem solved! Temporarily, at least...
Remember that the ants may come back; you'll have to repeat the process every now and then to keep them away.
Step 3: Plug Up Their Holes
If you follow the trail of ants, you'll find out where they're coming in. For me, the ants where feasting on the bread on our countertop, so they came in from the tiles on our kitchen wall through a hole in the tile. Spray the hole with the soapy water first, and then call in the caulking to seal it up. You can use grout, too. It's just my personal opinion that caulking is way more fun.
And if your little invaders are coming in from a hole in the drywall, just use joint compound to patch it up.
Hole in the cupboards? Use woodfiller. The list goes on and on. Those ants can chew their way through anything, it seems. Just use your better judgement when sealing their holes.
Step 4: You May Have Won the Battle...
Keep an empty spray bottle around in your garage, utility room, kitchen sink, wherever, just for spraying ants' tracks. They might keep coming back. Keep sealing their holes. If you think you may have a problem, either call an exterminator or relocate. ;]
Good luck, and I hope this helped!