To remove mould from walls and ceilings, start by protecting yourself with gloves and a mask. Open windows for ventilation and spray undiluted white vinegar directly on the mould. Let it sit for an hour, then wipe with a damp cloth and dry the area using a fan. Persistent mould in the same spot may indicate a leak or damp wall that requires professional attention. Avoid mixing cleaning products like vinegar and bleach, as this can release toxic gases.