ABS light on

I have the ABS light on and before taking the car to the stealership, I need to know if there is something I can do. I went to autozone and the won't check the ABS light, only the check engine light. Any ideas??
Thanx

Sometimes the light goes on after 2 minutes, sometimes after an hour.... It's weird.... If somebody has any suggestion it will be appreciated. Thanx again.

sounds like a bad abs sensor in one of the wheel bearings.