I'd take it in and have it scanned with a brake scanner to first find out where the problem is coming from. You will spend a lot of wasted time going from one end of the car to the other looking at all the possibilities that can trigger the light.
Unfortunately it isn't something that comes up with a normal scanner and you will usually get charged to get a reading.
The first things I look for if I'm not yet able to get a scan and can't wait is metal shavings on the magnetic abs sensor at the wheel and clean them off. Then I look over the sensor for any cracks that can let moisture in. Next I look at the "tone" ring to see if it has any missing teeth or a crack that can open the reading gap wider under different conditions of heat/cool to cause an erratic reading.
After that I'm off to a scanner.