Look for an acetane nail polish remover and soak them for several minutes. They will become gummy. Then take a stone or nail file and scrap off the gummy stuff. Then soak again and repeat til done. Takes some time and patience.
Some charge - some don't. Some won't if you're going to get new nails also. Soaking in the acetone takes a lot of time also but it does work. You might be able to find a stronger solution at a beauty supply store - maybe what the nail professionals use (if it's not regular acetone based polish remover). Trim them down as much as possible also and then soak until they get gummy like Kelly said!
Clarins makes a GREAT hand & nail treatment cream - use that afterwards too. It will help strengthen your nails. Oh - your nails might be tender for a bit after you remove the acrylics - just FYI!