The easiest way to recognize that your trailer has begun to skid is to:
Ask another driver.
Use your mirrors to determine if the trailer has left the lane.
Release the brake pedal and then push it down again.
Watch the jackknife warning light on the control panel.
The easiest way to spot a trailer skid is to use your mirrors. Any time you brake hard, check your mirrors to ensure that your trailer is still in its proper position.