Stop the pendulum's movement by gently grasping it and moving it into a neutral position. Remove the pendulum from the clock by lifting the pendulum rod free of the crutch's hook and carefully withdrawing it from the clock. Place the pendulum aside in a safe place during cleaning; be very careful to not bend the pendulum while moving it.
Move the clock away from the wall, being careful not to jostle it. Use a feather duster to remove any dust on the surfaces of the clock, especially the normally inaccessible rear of the casing.
Use a small dry vacuum to remove any dust or debris trapped in the cracks and crevices of the clock, including on the inside of the pendulum cabinet. Avoid bringing the vacuum near the sensitive mechanisms of the clock.
Clean any glass surfaces of the clock with a glass cleaner and soft paper towels, including the insides of the glass.
Move the clock back in place and use a leveling device to ensure that it is completely level. Reattach the pendulum by threading it through the eye of the crutch and securing it on the hook. Restart the pendulum and close any open doors on the clock.