Clock stops just before 1 o'clock. Caused by jamming of the strike mechanism behind the dial, and is usually accompanied by the strike not sounding. See that the strike weight is wound properly. Pull gently on the strike weight while moving the minute hand past the hour. This condition usually requires the attention of a clockmaker for a permanent fix.
Clocks stops within a few minutes.
Clock is probably out of beat. This is best corrected by a clockmaker. See if the pendulum is rubbing against the back of the case, and if so reposition the case so the back board is vertical or leans forward slightly. Clock stops at apparently random times. Check to see if the clock is wound properly.