Secure the pendulum and weights before moving anything. A pendulum left hanging swings against the suspension spring and can bend or break it; weights in a longcase must be removed, and the pendulum detached and carried separately.
Support a movement by its plates or seatboard, never by the escapement, hands or pendulum rod. A dial with a fragile surface should not be touched at all on the painted or silvered area.
Environment matters more than dusting. Stable moderate humidity protects wooden cases and prevents rust on steel parts; wide swings cause veneer lifting, joint failure and corrosion.
Avoid direct sunlight, exterior walls and heat sources. Sunlight fades painted dials and finishes irreversibly, and a case beside a radiator dries and splits.
Do not attempt cleaning with household products. Solvents, metal polishes and oils applied to dials, cases and movements remove original surfaces permanently; a clock needing attention should go to a qualified clockmaker or conservator.